Question

Who misses work more often at the ABC Company? Smokers or non-smokers? Test at .05 significance level. (3 Part Question)

Summary statistics are:

Smokers: Average number of days absent = 14.7; standard deviation = 5.0; n = 44

Non-Smokers: Average number of days absent = 8.3; standard deviation = 4.0; n = 60

A)

Suppose you want to do a 2-tailed test. What's the critical value and region of rejection?

Z = 1.96

Z = 1.645

Z > 1.96 or Z < -1.96

Z > 1.645 or Z < -1.645

B)

Suppose you want to do a 2-tailed test. What's the calculated value of the test statistic?

t = 0.7

t = 1.7

Z = 0.7

Z = 7.0

C)

Suppose you want to do a 2-tailed test. What's the conclusion?

We do not reject H0. There is a significant difference in mean number of absent days between the two groups.

We do not reject H0. There is not a significant difference in mean number of absent days between the two groups.

We reject H0. There is not a significant difference in mean number of absent days between the two groups.

We reject H0. There is a significant difference in mean number of absent days between the two groups.

Answer 1

A)

Critical value and region of rejection:

Z > 1.96 or Z < -1.96

B)

Calculated value of the test statistic:

Z = 7.0

C)

Conclusion:

We reject H0. There is a significant difference in mean number of absent days between the two groups.

Also, it can be seen that at the ABC company, smokers do not miss work more, since:

Here Z= 7 and Z(tab) = 1.645 (at 0.5 significance level)

So we reject the null hypothesis as for one-sided test, Z>Z(tab) is the rejection criterion.