4. An employee in a large corporation receives an average of 41.7 emails per day

Question

4. An employee in a large corporation receives an average of 41.7 emails per day. In an effort to reduce distraction caused by such interruptions, one company established a priority list that all employees were to use before sending an email. One month after the new priority list was put into place, company officials sought to determine if there had been a reduction in the average number of emails received per day per employee. A random sample of 50 employees showed that they were receiving an average of 36.2 emails per day. Suppose that the standard deviation of all emails is known to be 18.5.

What is the statistic of interest, what is the parameter of interest

b. Consider the previous problem. What are H0 and H1, the Null and Alternative Hypotheses, respectively?

6. Suppose that we want to test whether adding fluoride to toothpaste reduces the number of cavities. What is  a Type II error?

Explanation / Answer

4( a) Parameters are numbers that summarize data for an entire population. Statistics are numbers that summarize data from a sample, i.e. some subset of the entire population. Problems (1) through (6) below each present a statistical study*. For each study, identify both the parameter and the statistic in the study.

Statistic here is avearge 36.2 mails of 50 employees

Parameter = 41.7

b) H0: there had been a increase in the average number of emails received per day per employee

H1: there had been a reduction in the average number of emails received per day per employee

6) Type I and type II errors. ... In statistical hypothesis testing, a type I error is the incorrect rejection of a true null hypothesis (also known as a "false positive" finding), while a type II error is incorrectly retaining a false null hypothesis (also known as a "false negative" finding).

Here Null is: adding fluoride to toothpaste does not reduce the number of cavities

So, type 2 error will be assuming that adding fluoride to toothpaste does not reduce the number of cavities but in fact it does reduce the cavities.

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