A study was done to determine if the proportion of older drivers who use their seat belts differ from the proportion of younger drivers who use their seat belts. People were compared in the two age groups (16 - 24 years old and 25-69 years old). Of 1000 randomly selected 16-24 year olds, 79% said yes (they do always wear their seat belts). Of 1100 randomly selected 24-69 year olds, 84% said yes (they do always wear their seat belts). Below is the Minitab output. Test and Cl for Two Proportions
Method
pe = proportion where Sample 1 Event
px = proportion where Sample 2 Event
Difference pe - px
Descriptive Statistics
Sample N Event Sample P
Sample 1 1000 7900 70000
Sample 2 1100 934 0.840000
Estimation for Difference
90 Upper Bound for
Odference Difference
-0.05 0.028248
Based on sommation
Method Z-Value P. Value
Normal approximation 295 0002
Fisher's exact 0.002
The pooled estimate of the proportion e d for the
We are interested in testing if there sufficient evidence at the alpha = 0.10 level, to conclude that the two groups differ with respect to seat belts usage. Check the assumptions needed for this test.