CHAPTER 3 EXERCISES (Set 1)

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CHAPTER 3 EXERCISES (Set 1)
1. To estimate the mean of a population with unknown distribution shape and
unknownstandard deviation, we take a random sample of size 64. The sample mean is
24.2 andthe sample standard deviation is 4.8. Compute by hand and interpret a 90%
confidenceintervalforthe population mean. (Use Minitab to get the t multiplier.)
2. We are managing a large soy bean farm. To estimate our revenues for the
coming year, we need to estimate our crop yield. Soy bean yields are measured by
pods/plant. We are planning for a yield of 40 pods/plant. We take a random sample of
49 soy bean plants and get a sample mean yield of 40.9 pods/plant with a sample
standard deviation of 4.9 pods/plant. Use the sample to compute and interpret a 95%
confidence interval for our population yield. How comfortable should we be, based on
this interval, that we will have a yield of 40 pods/plant? (Use Minitab.)
3. A quality control specialist records the waiting times of 100 randomly selected
customers in the checkout lines of a large Indianapolis department store during a
recent holiday weekend. The data is recorded in the Minitab dataset: WaitingTimes.
Use Minitab to compute a 95% confidence for the waiting times for the store and give
an interpretation of this interval. (Hint: Use Stat -> Basic Statistics -> 1-Sample t)

2. 4. As quality control chief for Blotto Brewery, Inc., you wish to determine the
average calorie content of bottles of Blotto Lite. You randomly select 49 bottles off
the production line. They have an average calorie count of 102. The sample standard
deviation is 4.9 calories.
a. Compute by hand a 90% confidence interval based on this sample. (Use Minitab
to get the t multiplier.) Confirm your result with Minitab and give an interpretation of
this interval.
b. If we compute a 99% confidence interval based on this sample, will the margin of
error be larger or smaller than the margin of error for our 90% interval?