T Test For Two Independent Samples - Presentation Transcript

1. Week 9:Independent t -test t test for Two Independent Samples 1 2. Independent Samples t - test The reason for hypothesis testing is to gain knowledge about an unknown

population. Independent samples t-test is applied when we have two independent samples and want to make a comparison between two groups of individuals. The parameters are unknown. How is this different than a Z-test and One Sample t- test? 2

3. Independent t - test We are interested in the difference between two independent groups. As such, we are comparing two populations by evaluating the mean difference. In order to evaluate the mean difference between two populations, we sample from each population and compare the sample means on a given variable. Must have two independent groups (i.e.samples) and one dependent variable that is continuous to compare them on. 3

4. Examples: Do males and females significantly differ on their level of math anxiety? IV: Gender (2 groups: males and females) DV: Level of math anxiety Do older people exercise significantly less frequently than younger people? IV: Age (2 groups: older people and younger people) DV: Frequency of getting exercise 4

5. Examples: Do 8th graders have significantly more unexcused absences than 7th graders in Toledo junior highs? IV: Grade (2 groups: 8th grade and 7th grade) DV: Unexcused absences Note that Independent t-test can be applied to answer each research question when the independent variable is dichotomous with only two groups and the dependent variable is continuous. 5

6. Generate examples of research questions requiring an Independent Samples t-test: What are some examples that you can come up with? Remember- you need two independent samples and one dependent variable that is continuous. 6

7. Assumptions The two groups are independent of one another. The dependent variable is normally distributed. Examine skewness and kurtosis (peak) of distribution Leptokurtosis vs. platykurtosis vs. mesokurtosis The two groups have approximately equal variance on the dependent variable. (When n1 = n2 [equal sample sizes] ,the violation of this assumption has been shown to be unimportant.) 7

8. Steps in Independent Samples t-test 8 9. Step 1: State the hypotheses Ho: The null hypothesis states that the two samples come from the same

population. In other words, There is no statistically significant difference between the two groups on the dependent variable. Symbols: Non-directional: Ho: μ1 = μ2 Directional: H 0:µ ≥ µ1 2 or H 0:µ ≤ µ 1 2 • If the null hypothesis is tenable, the two group means differ only by sampling fluctuation – how much the statistic’s value varies from sample to sample or chance. 9

10. Ha: The alternative hypothesis states that the two samples come from different populations. In other words, There is a statistically significant difference between the two groups on the dependent variable. Symbols: Non-directional: H 1:µ ≠ µ 1 2 Directional: H 1:µ > µ 1 2 H 1:µ < µ 1 2 10

11. Step 2: Set a Criterion for Rejecting Ho Compute degrees of freedom Set alpha level Identify critical value(s) Table C. 3 (page 638 of text) 11

12. Computing Degrees of Freedom Calculate degrees of freedom (df) to determine rejection region. n n df = 1 + 2 − 2 -2 sample size for sample1+ sample size for sample2 • df describe the number of scores in a sample that are free to vary. • We subtract 2 because in this case we have 2 samples. 12

13. More on Degrees of Freedom • In an Independent samples t-test, each sample mean places a restriction on the value of one score in the sample, hence the sample lost one degree of freedom and there are n-1 degrees of freedom for the sample. 13

14. Set alpha level Set at .001, .01 , .05, or .10, etc. 14 15. Identify critical value(s) Directional or non-directional? Look at page 638 Table C.3. To determine your

CV(s) you need to know: df – if df are not in the table, use the next lowest number to be conservative directionality of the test alpha level 15

16. Step 3: Collect data and Calculate t statistic t= x −x 1 2 ( − 1) + ( − 1) 1 2 2 variance s n 1 1 s n + 1 2 2 n +n −2 n n 1 2 1 2 Whereby: n: Sample size s2 = variance df x :Sample mean subscript1 = sample 1 or group 1 subscript2 = sample 2 or group 2 16

17. Step 4: Compare test statistic to criterion df = 18 α = .05 , two-tailed test in this example • critical values are ± 2.101 in this example 17

18. Step 5: Make Decision Fail to reject the null hypothesis and conclude that there is no statistically significant difference between the two groups on the dependent variable, t = , p > α. OR Reject the null hypothesis and conclude that there is a statistically significant difference between the two groups on the dependent variable, t = , p < α. • If directional, indicate which group is higher or lower (greater, or less 18 than, etc.).

19. Interpreting Output Table: Mean APGAR Sample size SCORE Levene’s tests the assumption of equal variances – if p < .05, then variances t-value Degrees of are not equal and use a different test freedom to modify this: Here, we have met the assumption so use first row. CI p - value Observed difference 19 Retrieved on July 12, 2007 from SPSSShortManual.html between the groups

20. Interpreting APA table: 20 21. Variable Math anxiety t Gender Male 3.66 Female 3.98 3.35*** Age Under 40 years 3.32 Over 41 years 3.64

2.67** Note. **p < .01. ***p < .001. 21

22. Examples and Practice See attached document. Create the following index cards from this lecture: When to conduct a t-test (purpose, conditions, and assumptions) t-test statistic formula for computation t-test statistic formula df formula 22

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Definition

First step towards gaining an employees' commitment, it is aimed at

introducing the job and organization to the recruit and him or her to the

organization. It involves orientation and training of the employee in the

organizational culture, and showing how he or she is interconnected to

(and interdependent on) everyone else in the organization. See also

orientation.

  HomeAdvice and GuidanceAdvice A-ZHealth, work & wellbeingParents and carersEquality

Disputes and mediationRedundancy and noticeContracts and hoursPublications Appraisal related payAdvisory booklet - Employee appraisalAdvisory booklet - Employee

communications and consultationJob evaluationAdvisory booklet - Health Work and WellbeingAdvisory booklet - Pay systems Advisory booklet - Personnel data and record keepingAdvisory booklet - Recruitment and induction

IntroductionRecruitment and selection The recruitment processSelecting the best candidateReferences

and checkingInductionMonitoring effectivenessConclusionAppendix 1, 2 & 3NotesSuggested further readingAdvisory booklet - Redundancy handlingAdvisory booklet - Representation at workAdvisory booklet - Stress at workAdvisory booklet - Front line managersAdvisory booklet - Delivering Equality & DiversityAdvisory booklet - Teamwork: success through peopleAdvice leaflet - Bullying and harassment at work: a guide for managers and employersAdvice leaflet - Bullying and harassment at work: Guidance for employeesAdvice leaflet - Employing older workersAdvice leaflet - The right to apply for flexible working: A short guide for employers, working parents and carersAdvice leaflet - Holidays and holiday payAdvice leaflet - Internet and e-mail policiesAdvice leaflet - Lay-offs and short-time workingAdvice leaflet - Stress at workAdvice leaflet - Varying a contract of employmentAdvisory handbook - The A-Z of workAdvisory handbook - Discipline and grievances at workAdvisory handbook - Discipline and grievances at work (section 2 of 2)Advisory handbook - Employing people: a handbook for small firmsAdvisory handbook - Employing people: a handbook for small firms (section 2 of 2)Advisory booklet - Managing attendance and employee turnoverAdvisory booklet - Managing conflict at workAdvisory booklet - Flexible working and work-life balance Consultation on time off for trade union duties and activitiesAdvice leaflet - Managing in difficult timesSummaryHow we can help - Pre-Claim Conciliation explainedCode of Practice - Time off for trade union duties and activitiesAdvisory booklet - how to manage changeAdvisory booklet - how to manage performanceAdvisory booklet - The People Factor - engage your employees for business successAcas HelplineSocial NetworkingTools and ResourcesTraining and Business SolutionsHelp Resolving DisputesPrint

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Recruitment and selection

The importance of good recruitment and selection

Recruiting people who are wrong for the organisation can lead to increased labour turnover, increased costs for the organisation, and lowering of morale in the existing workforce. Such people are likely to be discontented, unlikely to give of their best, and end up leaving voluntarily or involuntarily when their unsuitability becomes evident. They will not offer the flexibility and commitment that many organisations seek. Managers and supervisors will have

to spend extra time on further recruitment exercises, when what is needed in the first place is a systematic process to assess the role to be filled, and the type of skills and abilities needed to fill it.

Most recruitment systems will be simple, with stages that can be followed as a routine whenever there is a vacancy to be filled, and which can be monitored and adapted in the light of experience.

This booklet describes the main features of such systems, and other related issues. Systems should be:

efficient - cost effective in methods and sources effective - producing enough suitable candidates without excess and ensuring the

identification of the best fitted for the job and the organisation fair - ensuring that right through the process decisions are made on merit alone.

The importance of fairness

The employer has the legal responsibility to ensure that no unlawful discrimination occurs in the recruitment and selection process on the grounds of sex, race, disability, age, sexual orientation, and religion or belief. Equality of opportunity is an integral part of the recruitment and selection process, and to this end employers may offer training and encouragement to any under-represented groups. Examples include pre-application assistance for those who do not have English as their first language, or management development training for women where they are under-represented in management grades (1).

Job advertisements may also state that the employer encourages applications from those groups that are under- represented in the organisation.

Employees and their representatives will also have an interest in fair, non-discriminatory recruitment and selection policies, and they should be fully consulted when new procedures are introduced or existing procedures reviewed. The Sex Discrimination Act 1975, the Race Relations Act 1976, the Employment Equality Regulations (covering sexual orientation, religion or belief, and age) and the Disability Discrimination Act 1995 set out the legal requirements for employers.

Organisations should be aware that the provisions of the Disability Discrimination Act 1995 not only make it unlawful to discriminate against disabled individuals without justifiable reason but also require employers to make reasonable adjustments to the workplace or working arrangements. Detailed guidance is available in the Code of Practice on the elimination of discrimination in employment. This can be obtained from The Stationery Office (2).

The Acas Equality Direct helpline (tel: 08456 00 34 44 begin_of_the_skype_highlighting              08456 00 34 44      end_of_the_skype_highlighting) can give advice on the best ways of implementing an equal opportunities policy.

Advice is also offered to employers in small and medium sized organisations through the Business Link service (4) and through Acas training (5).

Human resource planning

Recruiters need to keep abreast of changes in the labour market to ensure that their recruitment efforts are not wasted or directed at too small a pool of labour. Skill shortages may occur unexpectedly and recruitment and training processes need to be kept flexible. It is a good idea for any organisation to plan its labour force requirements, matching available supply against forecast demand. A skills audit of existing staff will increase knowledge of the skills the organisation has available and those which are lacking, and thus help pinpoint areas for future development.

A human resource plan need not be highly complicated. A straightforward plan will help organisations to:

assess future recruitment needs formulate training programmes develop promotion and career development policies anticipate and, where possible, avoid redundancies develop a flexible workforce to meet changing requirements control staff costs whilst ensuring salaries remain competitive assess future requirements for capital equipment, technology and premises.

Management is responsible for producing the human resource plan, senior management for supporting it. Implementation is likely to be most effective if it carries the support of the workforce, normally achieved through consultation with trade union or other employee representatives.

Producing a human resource plan involves:

forecasting staffing requirements against business objectives assessing the available supply of people to meet those requirements matching available supply against forecast demand (6).

Information on current employees, labour turnover and the labour market will help in the formulation of the plan. The Learning and Skills Council (visit www.lsc.gov.uk/)will be able to provide general information on the local labour market in England and on the skills balance available, as will the local Jobcentres. Local Education Authorities can assist with information on the numbers of school and college leavers.

Labour markets and the labour force

In times of changing labour markets, organisations need to adapt their recruitment and retention policies to allow them to compete more effectively for staff, particularly those with skills that are in short supply. The offer of training and development opportunities is often a strong attraction to potential recruits, and here again the Learning and Skills Council can offer advice and assistance. Jobcentres, which administer Government training schemes are another source of advice and potential recruits.

If recruitment is difficult in certain jobs or skills, consideration may need to be given to re-designing the job to make it a more attractive prospect - perhaps by offering a greater variety of tasks, or increased self-management. Employers also need to encourage a good 'work-life balance' within the organisation by giving consideration to more flexible ways of working. Employees with young and disabled children and the carers if adults, have the right to request flexible working arrangements - including job-sharing, part-time working, flexi-time, working from home/teleworking and school time contracts - and employers must have a good business reason for rejecting any application. Another possibility is to introduce some more flexible working arrangements, perhaps job-sharing, part-time working, flexi-time, working from home/teleworking, and school term-time contracts. These variations on the 'standard' forms of working will open the vacancy to people who might otherwise be unable to consider it. Equally, the offer of assistance with domestic care arrangements and costs can prove highly attractive to people with these responsibilities. Many companies are now offering 'family-friendly' policies. These are often developed in conjunction with local Business Links and Chambers of Commerce, which can provide examples of good practice.

The balance of the labour force is changing, with some increase in the numbers of women, young people, and most particularly older workers available for work. Employers are beginning to give serious consideration to the employment of older workers, and a voluntary Code of Practice to counteract ageism in employment has been introduced by the Government (7). Jobcentres will not accept vacancies with age limits.

The value of labour market information is that it gives employers some forecasts from which they can decide how best to plan for future recruitment. Should the organisation make a positive move to attract older workers? What might best be done to counter any shortage of potential recruits with particular skills? Should training new and existing workers move higher up the priority list in the firm?

Should the organisation make the introduction of family-friendly policies a priority so as to attract the widest range of suitable staff? Looking at all the options means that recruitment will be better targeted and therefore more efficient and effective.

Recruitment and selectionA Tesco case study

Page 1: Introduction

Tesco is the biggest private sector employer in the UK. The company has more than 360,000 employees worldwide. In the UK, Tesco stores range from small local Tesco Express sites to large Tesco Extras and superstores. Around 86% of all sales are from the UK.

Tesco also operates in 12 countries outside the UK, including China, Japan and Turkey. The company has recently opened stores in the United States. This international expansion is part of Tesco”s strategy to diversify and grow the business.

In its non-UK operations Tesco builds on the strengths it has developed as market leader in the UK supermarket sector. However, it also caters for local needs. In Thailand, for example, customers are used to shopping in “wet markets” where the produce is not packaged. Tesco uses this approach in its Bangkok store rather than offering pre-packaged goods as it would in UK stores.

Tesco needs people across a wide range of both store-based and non-store jobs:

In stores, it needs checkout staff, stock handlers, supervisors as well as many specialists, such as pharmacists and bakers.

Its distribution depots require people skilled in stock management and logistics. Head office provides the infrastructure to run Tesco efficiently. Roles here include

human resources, legal services, property management, marketing, accounting and information technology.

Tesco aims to ensure all roles work together to drive its business objectives.

Tesco needs to ensure it has the right number of people in the right jobs at the right time. To do this, it has a structured process for recruitment and selection to attract applicants for both managerial and operational roles.

Workforce planning is the process of analysing an organisation”s likely future needs for people in terms of numbers, skills and locations. It allows the organisation to plan how those needs can be met through recruitment and training. It is vital for a company like Tesco to plan ahead. Because the company is growing, Tesco needs to recruit on a regular basis for both the food and non-food parts of the business.

Positions become available because:

jobs are created as the company opens new stores in the UK and expands internationally

vacancies arise as employees leave the company when they retire or resign or get promotion to other positions within Tesco

new types of jobs can be created as the company changes its processes and technology

Tesco uses a workforce planning table to establish the likely demand for new staff. This considers both managerial and non-managerial positions.

In 2008/09, for example, Tesco calculates that to support its business growth there will be a demand for around 4,000 new managers.

The planning process

This planning process runs each year from the last week in February. There are quarterly reviews in May, August and November, so Tesco can adjust staffing levels and recruit where necessary. This allows Tesco sufficient time and flexibility to meet its demands for staff and allows the company to meet its strategic objectives, for example, to open new stores and maintain customer service standards.

Tesco seeks to fill many vacancies from within the company. It recognises the importance of motivating its staff to progress their careers with the company. Tesco practises what it calls “talent planning”. This encourages people to work their way through and up the organisation. Through an annual appraisal scheme, individuals can apply for “bigger” jobs. Employees identify roles in which they would like to develop their careers with Tesco. Their manager sets out the technical skills, competencies and behaviours necessary for these roles, what training this will require and how long it will take the person to be ready to do the job. This helps Tesco to achieve its business objectives and employees to achieve their personal and career objectives.

Job descriptions and person specifications

An important element in workforce planning is to have clear job descriptions and person specifications. A job description sets out:

the title of the job to whom the job holder is responsible for whom the job holder is responsible a simple description of roles and responsibilities

A person specification sets out the skills, characteristics and attributes that a person needs to do a particular job.

Together, job descriptions and person specifications provide the basis for job advertisements. They help job applicants and post-holders to know what is expected of them. As they are sent to anyone applying for jobs, they should:

contain enough information to attract suitable people act as a checking device to make sure that applicants with the right skills are chosen

for interview

set the targets and standards for job performance

At Tesco these documents are combined:

Job descriptions and person specifications show how a job-holder fits into the Tesco business. They help Tesco to recruit the right people. They also provide a benchmark for each job in terms of responsibilities and skills. These help managers to assess if staff are carrying out jobs to the appropriate standards

Skills and behaviours

Tesco”s purpose is to serve its customers.

Tesco's organisational structure has the customer at the top. Tesco needs people with the right skills at each level of this structure.

There are six work levels within the organisation. This gives a clear structure for managing and controlling the organisation. Each level requires particular skills and behaviours.

Work level 1 frontline jobs working directly with customers. Various in-store tasks, such as filling shelves with stock. Requires the ability to work accurately and with enthusiasm and to interact well with others.

Work level 2 leading a team of employees who deal directly with customers. Requires the ability to manage resources, to set targets, to manage and motivate others.

Work level 3 running an operating unit. Requires management skills, including planning, target setting and reporting.

Work level 4 supporting operating units and recommending strategic change. Requires good knowledge of the business, the skills to analyse information and to make decisions, and the ability to lead others.

Work level 5 responsible for the performance of Tesco as a whole. Requires the ability to lead and direct others, and to make major decisions.

Work level 6 creating the purpose, values and goals for Tesco plc. Responsibility for Tesco”s performance. Requires a good overview of retailing, and the ability to build a vision for the future and lead the whole organisation.

Tesco has a seven-part framework that describes the key skills and behaviours for each job at every level in the company. This helps employees understand whether they have the right knowledge, skills or resources to carry out their roles.

Attracting and recruiting

Recruitment involves attracting the right standard of applicants to apply for vacancies. Tesco advertises jobs in different ways. The process varies depending on the job available.

Internal recruitment

Tesco first looks at its internal Talent Plan to fill a vacancy. This is a process that lists current employees looking for a move, either at the same level or on promotion. If there are no suitable people in this Talent Plan or developing on the internal management development programme, Options, Tesco advertises the post internally on its intranet for two weeks.

External recruitment

For external recruitment, Tesco advertises vacancies via the Tesco website www.tesco-careers.com or through vacancy boards in stores. Applications are made online for managerial positions. The chosen applicants have an interview followed by attendance at an assessment centre for the final stage of the selection process. People interested in store-based jobs with Tesco can approach stores with their CV or register though Jobcentre Plus. The store prepares a waiting list of people applying in this way and calls them in as jobs become available.

For harder-to-fill or more specialist jobs, such as bakers and pharmacists, Tesco advertises externally:

through its website and offline media through television and radio by placing advertisements on Google or in magazines such as The Appointment

Journal

Tesco will seek the most cost-effective way of attracting the right applicants. It is expensive to advertise on television and radio, and in some magazines, but sometimes this is necessary to ensure the right type of people get to learn about the vacancies.

Tesco makes it easy for applicants to find out about available jobs and has a simple application process.

By accessing the Tesco website, an applicant can find out about local jobs, management posts and head office positions. The website has an online application form for people to submit directly. Selection

Selection involves choosing the most suitable people from those that apply for a vacancy, whilst keeping to employment laws and regulations. Screening candidates is a very important part of the selection process. This ensures that those selected for interview have the best fit with the job requirements.

Screening

In the first stages of screening, Tesco selectors will look carefully at each applicant”s curriculum vitae (CV). The CV summarises the candidate”s education and job history to date. A well-written and positive CV helps Tesco to assess whether an applicant matches the person specification for the job.

The company also provides a “job type match” tool on its careers web page. People interested in working for Tesco can see where they might fit in before applying.

The process Tesco uses to select external management candidates has several stages.

Assessment centres

A candidate who passes screening attends an assessment centre. The assessment centres take place in store and are run by managers. They help to provide consistency in the selection process. Applicants are given various exercises, including team-working activities or problemsolving exercises. These involve examples of problems they might have to deal with at work.

Candidates approved by the internal assessment centres then have an interview. Line managers for the job on offer take part in the interview to make sure that the candidate fits the Conclusion

Workforce planning is vital if a business is to meet its future demands for staff. It allows a business time to train existing staff to take on new responsibilities and to recruit new staff to fill vacancies or to meet skill shortages.

Tesco is a major international company with many job opportunities, including management, graduate, school leaver and apprentice posts. 

Tesco needs to have people with the right skills and behaviours to support its growth and development.

Tesco has clear organisational structures, detailed job descriptions and person specifications. It provides user-friendly ways of applying for jobs and a consistent approach to recruitment and selection. This means it can manage its changing demand for staff.

job requirements.

Developing appropriate leadership stylesA Tesco case study

Page 1: Introduction

Tesco is a customer-oriented business. It aims to offer products that provide value for money for its customers and to deliver high-quality service. Tesco wants to attract new customers, but it also wants to keep its existing customers happy. Building customer loyalty is a cost-effective strategy to grow the business. This is because satisfied customers are a good advert for the business.

Tesco has more than a 30% market share of the UK grocery market, nearly double that of its nearest rival. In its 2009/2010 financial year, Tesco earned revenues of £38.6 billion in the UK and employed more than 280,000 people. To keep at the top of its game and to maintain its number one spot in the market, the company needs skilled staff at all levels and in all roles.

Roles in Tesco

Roles in Tesco range from business development, supply chain management and marketing to finance, store operations and personnel management. Each area of expertise requires

leadership and management skills. Tesco aims to develop the leadership qualities of its people throughout the organisation, from administrators and customer assistants to the board of directors. It adopts a similar approach to leadership development for staff at all levels. This is in line with Tesco’s employment philosophy: ‘We believe in treating each other with respect, with everyone having an equal opportunity to get on, ensuring Tesco is a great place to work.’

This case study will show how Tesco’s leadership framework is fundamental to developing the qualities of leadership needed at every level in the business.

Tesco | Developing appropriate leadership styles