Means student version

# Means student version - Data Analysis: T-tests Professor...

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© 2011 Robert H. Smith School of Business University of Maryland Data Analysis: T-tests Professor Whitney Professor Whitney

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© 2011 Robert H. Smith School of Business University of Maryland T-Tests We’ll discuss three t-tests (there are more types): t-test of a single mean (1 interval or ratio variable) Is there a significant difference between the sample mean and an expected value (mean)? Example: Has the mean value of attitude toward Jason’s Deli changed since last year’s survey? Independent samples t-test (1 interval or ratio variable and 1 nominal variable identifying 2 groups) Is there a significant difference between the mean associated with 1 variable for 2 different groups. • Example: Are there differences between married couples and unmarried people in terms of the number of nights they eat out per week? Is there a relationship between marital status and number of nights eaten out? t-test of a Proportion Is there a significant difference between the sample proportion and the expected proportion (hypothesized proportion)? • Example: Was the market share in the test market significantly different from the expected market share?
© 2011 Robert H. Smith School of Business University of Maryland Z-test vs. T-test Z-Test: Hypothesis test used for testing means if the sample is large enough (usually samples of 30+), drawn from a normal population, and where the population standard deviation is known. t-Test: Hypothesis test used for means if the sample is too small (< 30) to use the Z-test or if the population standard deviation is unknown.

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© 2011 Robert H. Smith School of Business University of Maryland Formula for T-Test of a Single Mean (referred to as Tobs or Tcalc) x s x t μ - = x Where: X S = sample mean = hypothesized population mean = standard error of the mean Degrees of Freedom = n-1
© 2011 Robert H. Smith School of Business University of Maryland T-test Decision Rules

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## This note was uploaded on 09/07/2011 for the course BMGT 452 taught by Professor Staff during the Spring '08 term at Maryland.

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Means student version - Data Analysis: T-tests Professor...

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