Question

A national firm reports mean earnings of $69 ± $12 (μ ± σ) per unit sold over the lifetime of the company. A competing company over the past 25 reporting periods had reported mean earnings equal to $71 per unit sold. Conduct a one-sample z-test to determine whether mean earnings (in dollars per unit) are larger (compared to that reported by the national firm) at a 0.05 level of significance.

(a) State the value of the test statistic. (Round your answer to two decimal places.) z =

State whether to retain or reject the null hypothesis.

Retain the null hypothesis. Reject the null hypothesis.

(b) Compute effect size using Cohen's d. (Round your answer to two decimal places.) d =

Answer 1

given data are:-

sample mean () = 71

sample size (n) = 25

population mean () = 69

population sd () = 12

a).hypothesis:-

test statistic be:-

p value :-

[ from standard normal table]

decision:-

p value = 0.2033 >0.05 (alpha)

so, we retain (fail to reject) the null hypothesis.

b). effect size be:-

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