let's calculate na 2.0

Intro

Let's Calculate NASpecial thanks to my beautiful wife, family and friends.

Biostatistics TeamMohamad Adam Bin Hj. Bujang(2007)Abdul Muneer Abdul Hamid(2008)Premaa a/p Supramaniam(2009)Tassha Hilda Adnan(2009)Nurina Musta'ani Bt Hamedon(2009)Siti Sara Bt Mat Lazim(2010)Mariana Bt Mohamad Ali(2011)Nor Aizura Bt Zulkifli(2011)Shahrul Aiman Bin Soelar(2011)Evi Diana Omar(2012)Nurakmal Baharum(2012)Nadiah Binti Saat(2013)Tg Mohd Ikhwan B. Tg Abu Bakar Sidik(2013)

Developed by sir-NAPLEASE USE AND SHARE WITH OTHERS

Katakanlah: Sesungguhnya sembahyangku, ibadatku, hidupku dan matiku, hanyalah untuk Allah, Tuhan yang memelihara dan mentadbirkan sekalian Alam. (Maksud Surah Al-Anam ayat 162)

Sample Size Guidelines

Pilot Study

Description:Julious (2005) recommends a minimum sample size of 12 per group as a rule of thumb and justifies this based on rationale about feasibility and precision about the mean and variance.Suggested citation:Julious SA. Sample size of 12 per group rule of thumb for a pilot study. Pharmaceutical Statistics 2005 4(4):287-91.

Description:Sim and Lewis (2012) suggest a sample size of at least 50 per group.Suggested citation:Sim J, Lewis M: The size of a pilot study for a clinical trial should be calculated in relation to considerations of precision and efficiency. J Clin Epidemiol 2012, 65:301-308.

Compare 2 groups (Means)

Unpaired t-test/Independent t-testTest using IBM SPSS Statistics for WindowsOpen the file "Pilot Study (Compare Mean G).sav"Type of data:NumericalAnalyze >> Descriptive Statistics >> ExploreSignificant level ():0.05Power (1-):0.80Group 1Group 2

ObjectiveMeanSDMeanSDSample Size Per GroupEXAMPLE41.6704.59040.2204.055141140.0334157.30122.771.2.3.4.Note: SD = Standard DeviationDrop-out:20%00.00

Corrected Sample Size Per Group:0.0

Description:Sample size estimation was performed using two population means formulae (Lemeshow, Hosmer, Klar, Lwanga, & Organization, 1990). Prior data indicate that the mean and standard deviation of {Objective} of the {Group 1} group are {Mean in Group 1} and {SD in Group 1}, respectively. If the mean and standard deviation of {Group 2} group are {Mean in Group 2} and {SD in Group 2}, we will need to study {Sample Size Per Group} samples per group to be able to reject the null hypothesis with probability (power) 0.8. The Type I error probability associated with this test of this null hypothesis is 0.05. We will use an independent t-test statistic to evaluate this null hypothesis. With an additional of 20% dropout rate, the sample size is {Corrected Sample Size Per Group} samples per group.

Output

Hypothesis (Equality)

Formulae for Sample Size Calculations

ReferencesLemeshow S., Hosmer D. W., Klar J., Lwanga S. K., & Organization W. H. (1990). Adequacy of sample size in health studies. Retrieved from http://apps.who.int//iris/handle/10665/41607

Compare 2 times (Means)

Paired t-test/Dependent t-testTest using IBM SPSS Statistics for WindowsOpen the file "Pilot Study (Compare Mean T).sav"Type of data:NumericalAnalyze >> Descriptive Statistics >> ExploreSignificant level ():0.05Power (1-):0.80Time 1Time 2

ObjectiveMeanSDMeanSDSample SizeEXAMPLE41.6704.59040.2204.0557978.649778.6561.381.0.00002.0.00003.0.00004.0.0000Note: SD = Standard DeviationDrop-out:20%00.00

Corrected Sample Size:0.0

Description:Sample size estimation was performed using the population means formulae (Lemeshow, Hosmer, Klar, Lwanga, & Organization, 1990). Prior data indicate that the mean and standard deviation of {Objective} of the {Time 1} are {Mean in Time 1} and {SD in Time 1}, respectively. If the mean and standard deviation of {Time 2} are {Mean in Time 2} and {SD in Time 2}, we will need to study {Sample Size} samples to be able to reject the null hypothesis with probability (power) 0.8. The Type I error probability associated with this test of this null hypothesis is 0.05. We will use an Paired t-test statistic to evaluate this null hypothesis. With an additional of 20% dropout rate, the sample size is {Corrected Sample Size} samples.

Output




Compare 2 groups (Proportions)

Pearson Chi-square test/Fisher's exact testTest using IBM SPSS Statistics for WindowsOpen the file "Pilot Study (Compare Proportion G).sav"Type of data:CategoricalAnalyze >> Descriptive Statistics >> CrosstabsSignificant level ():0.05Power (1-):0.80Group 1Group 2

ObjectiveProportionProportionSample Size Per GroupEXAMPLE0.8000.667173172.28931.2.3.4.

Drop-out:20%00.00

Corrected Sample Size Per Group:0.0

Description:Sample size estimation was performed using two population proportions formulae (Lemeshow, Hosmer, Klar, Lwanga, & Organization, 1990). Prior data indicate that the proportion of {Objective} of the {Group 1} group is {Proportion in Group 1}. If the proportion of {Group 2} group is {Proportion in Group 2}, we will need to study {Sample Size} samples to be able to reject the null hypothesis with probability (power) 0.8. The Type I error probability associated with this test of this null hypothesis is 0.05. We will use an Pearson Chi-square test to evaluate this null hypothesis. With an additional of 20% dropout rate, the sample size is {Corrected Sample Size} samples.

Output




1 groups (Proportions)

Descriptive StatisticsTest using IBM SPSS Statistics for WindowsOpen the file "Pilot Study (Compare Proportion G).sav"Type of data:CategoricalAnalyze >> Descriptive Statistics >> FrequenciesSignificant level ():0.05Precision:0.10

ObjectiveProportionPopulation SizeSample SizeEXAMPLE0.7337675.18161.gait, balance & fear of falling0.3008180.67062.0.00003.0.00004.0.0000

Drop-out:20%81101.25


Description:Sample size estimation was performed using the population proportion formulae (Lemeshow, Hosmer, Klar, Lwanga, & Organization, 1990). Prior data indicate that the proportion of {Objective} is {Proportion}. If the Type I error probability and precision are 0.05 and {Precision}, we will need to study {Sample Size} samples. With an additional of 20% dropout rate, the sample size is {Corrected Sample Size} samples.

Output


Without Finite Population Correction:

With Finite Population Correction:


Exploratory Factor Analysis

Relibility Analysis/Exploratory Factor AnalysisDepression Anxiety and Stress Scale (DASS)

ObjectiveNumber of QuestionsNumber of ScalesRule of ThumbSample SizeEXAMPLE2141:3631.mix15111:3452.3.4.Note: Numerical and Mix scale code as 1 and 11, respectively.Drop-out:20%4556


Description:The questionnaire consisted of {Number of Questions} questions related to {Objective}. A {Number of Scales}-point Likert scale will be used, ranging from {Minimum of Scale} = {Definition of Scale} to {Maximum of Scale} = {Definition of Scale}. For reliability and exploratory factor analysis purposes, Bujang, Ghani, Soelar and Zulkifli (2012) emphasised {Rule of Thumb} as rule of thumb to calculate the sample size. With an additional of 20% drop out rate, the sample size is {Corrected Sample Size} samples.

GUIDELINE TO USE MINIMUM SAMPLE SIZE

ReferencesBujang Mohamad Adam, Ghani Puzziawati Ab, Soelar Shahrul Aiman, Zulkifli Nor Aizura. Sample size guideline for exploratory factor analysis when using small sample: Taking into considerations of different measurement scales, Statistics in Science, Business, and Engineering (ICSSBE), 2012. doi: 10.1109/ICSSBE.2012.6396605

let's calculate na 2.0

Documents