Davenport University STAT219 – Lab #3

( Qu es tion # 4 )

Davenport University STAT219 – Lab #3

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The following problems are to be written up in polished form, showing all relevant work. I'm big on partial credit so I need to see what you're doing. Be sure to use correct notation and clearly convey your ideas.

When you are ready for the problems in this section to be graded, submit them to me as an attachment via the assignment manager. Please use the following conventions for your file name. Lab2-Your First and Last Name (e.g., Lab2–JaneDoe)

Please copy the answers you get from Minitab into the Word Document you submit for grading. “Polished form” means that you are properly labeling your final answers (e.g., for Question #1a, your answer should read something like, “The mean of the cookie weights is X ounces and the median is Y ounces.”

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Question # 1

In 1990, 5.8% of job applicants who were tested for drugs failed the test.

A random sample of 1440 current job applicants results in 61 failures (based loosely on data from the American Management Association).

At the α = 0.01 significance level, test the below claim (i.e., that the failure rate is now lower)

HO: p = 0.058

HA: p < 0.058

a) Is this an upper tail, lower tail, or two-tail test? (5 points)

b) Are we testing means or proportions? (5 points)

c) State the rule of rejection (in terms of p-value and level of significance) (5 points)

d) Find the p-value (5 points)

e) Should you reject or not reject HO? (5 points)

f) Does the result suggest that fewer job applicants now use drugs? (5 points)

Researchers studying infant head circumferences (in centimeters) wish to test if the mean head circumference differs from the historical mean of 34.5 cm. The researchers obtain a sample of 17 infants with a mean head circumference of 34.16 cm and a standard deviation of 0.58 cm.

At the α = 0.05 significance level, test the claim

HO: µ = 34.5

HA: µ ≠ 34.5

a) Is this an upper tail, lower tail, or two-tail test? (5 points)

b) Are we testing means or proportions? (5 points)

c) State the rule of rejection (in terms of p-value and level of significance) (5 points)

d) Find the p-value (5 points)

e) Should you reject or not reject HO? (5 points)

f) Does the result suggest that the mean head circumference differs from 34.5 cm? (5 points)

Question # 3

Perform the following hypothesis test on the paired data below:

HO: µd = 0 (Please recall that µd is read ~ and also known as ~ Mu-sub-d) HA: µd ≠ 0 Test at α = 0.05

Before	30	72	97	59	61	57	57	89	92
After	57	68	98	62	67	71	68	96	98

a) Is this an upper tail, lower tail, or two-tail test? (5 points)

b) Are we testing means or proportions? (5 points)

c) State the rule of rejection (in terms of p-value and level of significance) (5 points)

d) Find the p-value (5 points)

e) Should you reject or not reject HO? (5 points)

f) Do the data provide sufficient evidence to suggest the After scores are indeed higher? Why or why not? (5 points)

Note: Because the above is a two-tail test, rejection of Ho alone is not a sufficient reason. Hint: What else did you observe among the sample results?

( Qu es tion # 2 )

The below sample data represents the cost of 9 name-brand drugs and their corresponding generic equivalent. (Use Name Brand as Sample1 )

Name Brand	120	150	135	140	160	175	140	120	165
Generic Brand	99	135	130	119	139	150	129	109	160

a) Compute a two-sided 90% confidence Interval estimate for µd. (5 points)

b) Based on your interval, can you safely conclude that generics are less expensive than name brand? Why or why not? (5 points)