Employees at ABC corporation receive an average of µ = 41.7 emails per day with

Question

Employees at ABC corporation receive an average of µ = 41.7 emails per day with a standard deviation of = 18.5 emails per day. Recently the company's network was under attack and the employees started receiving a lot of unwanted email (SPAM). A random sample of 45 employees showed they now receive an average of 47.2 emails per day. At the 5% level of significance, does the attack represent a significant increase in emails received by the employees?

A. Yes, the attack represents a significant increase in emails received by the employees. We know this because the test statistic is in the rejection region.

Explanation / Answer

For this we have to test the null hypothesis H0: Mu=41.7 verssu the alternative H1: Mu>41.7

We are given sample mean x_bar=47.2, sample size n=45 and population standard deviation sigma=18.5

Test statistic Z=(x_bar-Mu)/[sigma/sqrt(n)]

=(47.2-41.7)/[18.5/sqrt(45)]

=1.9943

Right tailed critical value at 5% level is =1.645

As calculated Z>1.645, we reejct the null hypothesis and conclude that

Part-A is the correct answer

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