Question

An insurance company collects data on​ seat-belt use among drivers in a country. Of 1300 drivers 30-39 years​ old, 22​% said that they buckle​ up, where as 384 of 1200 drivers 55-64 years old said that they did. At the 10% significance​ level, do the data suggest that there is a difference in​ seat-belt use between drivers 30-39 years old and those 55-64?

Calculate the test statistic

z=

Answer 1

Ans:

sample peoportion 1 =0.22

sample peoportion 2 =384/1200=0.32

pooled proportion=(0.22*1300+384)/(1300+1200)=0.268

Test statistic:

z=(0.22-0.32)/sqrt(0.268*(1-0.268)*((1/1300)+(1/200)))

z=-2.97