QM 2113 - Spring 2002QM 2113 - Spring 2002

Statistics for Statistics for Decision MakingDecision Making

Excel for Excel for Statistics: An Statistics: An

OverviewOverview

Student ObjectivesStudent Objectives

Perform basic Excel tasksPerform basic Excel tasks– Building formulae– Copy/paste– Insert rows/columns– Move– Modify displays

Use Excel functions for basic statisticsUse Excel functions for basic statistics– Descriptives: mean, median, standard deviation,

quantiles – Integrate with presentation features

Summarize guidelines for spreadsheet Summarize guidelines for spreadsheet design and developmentdesign and development

First, . . . First, . . .

Turn in your homeworkTurn in your homework– Histograms– Bar charts– Quantiles for KIVZ– Old stuff (look at the roster)

• eMail address• Questionnaire info

Monday: meet in BU 221Monday: meet in BU 221

Here’s an ExerciseHere’s an Exercise

Goal: Goal: – Demonstrate Excel formulae and display

concepts– Application to data analysis– But not a demo of Excel’s statistics capability

Given income values:Given income values:$76,723$37,452$22,557$60,155

Calculate average & standard deviationCalculate average & standard deviation Create attractive tabular displayCreate attractive tabular display

Working the Exercise Working the Exercise (Quick & Dirty)(Quick & Dirty)

Column A: type values (no $ or comma)Column A: type values (no $ or comma) Use Excel’s Use Excel’s tool to sum values tool to sum values Divide sum by n (use COUNT, not 4)Divide sum by n (use COUNT, not 4) Column B: subtract x-bar (use absolute Column B: subtract x-bar (use absolute

addressing) from first x valueaddressing) from first x value Copy result down 3 cellsCopy result down 3 cells Column C: square first deviation and Column C: square first deviation and

copy result down 3 cellscopy result down 3 cells Sum squared deviationsSum squared deviations Divide result by n-1Divide result by n-1 Take square root of the resultTake square root of the result

Working the Exercise Working the Exercise (Cleaning it Up)(Cleaning it Up)

Insert four rows at top and 1 column at Insert four rows at top and 1 column at leftleft

Create column headingsCreate column headings Center, boldface, and italicize column Center, boldface, and italicize column

headingsheadings Adjust column widthsAdjust column widths Format raw data values as currency with Format raw data values as currency with

0 decimal places0 decimal places Format intermediate calculations Format intermediate calculations

appropriatelyappropriately Add appropriate labels for x-bar and sAdd appropriate labels for x-bar and s Create an overall centered title for tableCreate an overall centered title for table

Now, Let’s Use Excel Now, Let’s Use Excel More EfficientlyMore Efficiently

KIVZ data: analysis of McCall KIVZ data: analysis of McCall incomesincomes

Download dataset from the WebDownload dataset from the Web– Don’t open within browser– Instead, save to disk and then open in

Excel Enter data into Column A (type Enter data into Column A (type

or copy from original worksheet)or copy from original worksheet)

Using Excel’s Built-In Using Excel’s Built-In FunctionsFunctions

Summarize central tendencySummarize central tendency– Mean (AVERAGE)– Median (MEDIAN)

Summarize spreadSummarize spread– Standard deviation (STDEV)– Range (MAX and MIN)

Calculate alsoCalculate also– Percentiles– Cumulative frequency

Spreadsheet Spreadsheet GuidelinesGuidelines

Save your work often (once per step)Save your work often (once per step) Keep in mind that spreadsheets are Keep in mind that spreadsheets are

typically reusedtypically reused– Updated data– Modified to fit similar situations– Use Data Analysis tool only as quick & dirty

Avoid using constants in formulaeAvoid using constants in formulae Keep data separate from cells with Keep data separate from cells with

calculationscalculations Consider locking cells involving Consider locking cells involving

calculationscalculations Do whatever it takes not to type dataDo whatever it takes not to type data

Odds & EndsOdds & Ends

Inference examplesInference examples– Hypothesis testing– Estimation

Some notes on variationSome notes on variation– What’s a “variance”?– The CV: answering the question “How much is

much?”– Where is the variation?

• Median versus mean• Skew• Using the histogram to address this question

Discrepancies in quantile computationsDiscrepancies in quantile computations

HomeworkHomework

Use Excel to calculate average Use Excel to calculate average income and standard deviation income and standard deviation for Channel 6 as demonstrated for Channel 6 as demonstrated in first exercisein first exercise

Use Excel statistical functions to Use Excel statistical functions to calculate descriptive statistics calculate descriptive statistics for overall McCall viewing timefor overall McCall viewing time

More info to be posted at More info to be posted at websitewebsite