Question

Hypothesis Tests with Z-statistics

1. Before making a commercial, customers at a bakery purchased an average of $451 in products per month, with a standard deviation of $102. After the commercial aired, 43 customers came into the bakery the next month and purchased an average of $502 products that month.

a. Who are the groups being compared/tested?
b. What are the null and research hypotheses?
c. what are the numbers needed for the z statistic?
d. What is the z statistic?
e. For a two tailed test at .05 significance, the critical area is +/- 1.96. What decision do we make?

Answer 1

Solution :

= 502

=451

=102

n = 43

b ) This is the two tailed test .

The null and alternative hypothesis is ,

H0 :    = 502

Ha :     502

c ) Test statistic = z

= ( - ) / / n

= (451-502) / 102 / 43

= -3.28

d )Test statistic = z = -3.28

P(z < -3.28) =  0.0005

P-value = 2 *0.0005 =0.0010

= 0.05  

P-value <

0.0010<0.05

e ) A two tailed test at .05 significance, the critical area is +/- 1.96.

Reject the null hypothesis .

There is sufficient evidence to suggest that