1 / 25

Differences Between Group Means

Differences Between Group Means. (Click icon for audio). Differences between Groups when Comparing Means. Interval or ratio scaled variables t-test When groups are small When population standard deviation is unknown z-test When groups are large.

yuma
Télécharger la présentation

Differences Between Group Means

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Differences Between Group Means (Click icon for audio) Dr. Michael R. Hyman, NMSU

  2. Differences between Groups when Comparing Means • Interval or ratio scaled variables • t-test • When groups are small • When population standard deviation is unknown • z-test • When groups are large

  3. Null Hypothesis about Mean Differences between Groups

  4. X1 = mean for Group 1 X2 = mean for Group 2 SX1-X2 = the pooled or combined standard error of difference between means t-Test for Difference of Means

  5. Pooled Estimate of the Standard Errort-test for the Difference of Means S12 = the variance of Group 1 S22 = the variance of Group 2 n1 = the sample size of Group 1 n2 = the sample size of Group 2

  6. t-Test for Difference of Means Example

  7. Comparing Two Groups when Comparing Proportions • Percentage Comparisons • Sample Proportion - P • Population Proportion -

  8. Differences between Two Groups when Comparing Proportions The hypothesis is: Ho: P1 = P2 may be restated as: Ho: P1 - P2 = 0

  9. Z-Test for Differences of Proportions p1 = sample portion of successes in Group 1 p2 = sample portion of successes in Group 2 (p1 - p1)= hypothesized population proportion 1 minus hypothesized population proportion 1 minus Sp1-p2 = pooled estimate of the standard errors of difference of proportions

  10. Z-Test for Differences of Proportions: Standard Deviation p= pooled estimate of proportion of success in a sample of both groups p= (1- p) or a pooled estimate of proportion of failures in a sample of both groups n1 = sample size for group 1 n2 = sample size for group 2

  11. Z-Test for Differences of Proportions: Example

  12. Z-Test for Differences of Proportions

  13. Z-Test for Differences of Proportions: Example

  14. Hypothesis Test of a Proportion p is the population proportion p is the sample proportion p is estimated with p

  15. Hypothesis Test of a Proportion p = H : . 5 0 p ¹ H : . 5 1

  16. = n 1 , 200 = p . 20 pq = S p n (. 2 )(. 8 ) = S p 1200 . 16 = S p 1200 = S . 000133 p = S . 0115 p Hypothesis Test of a Proportion: Another Example

  17. The Z value exceeds 1.96, so the null hypothesis should be rejected at the .05 level. it is significant t beyond the .001 Hypothesis Test of a Proportion: Another Example - p p = Z S p - . 20 . 15 = Z . 0115 . 05 = Z . 0115 = Z 4 . 348 Indeed

More Related