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# Solving Multiple Questions on Descriptive Statistics

1. Determine whether the description corresponds to an observational study or an experiment.
Forty patients with skin cancer are divided into two groups. One group an experimental drug to fight cancer, the other a placebo. After two years, the spread of the cancer is measured.

Does the description correspond to an observational study or experiment?

2. A worker assembles one item every 20 minutes, so 120 items are completed in her first week of work. Her manager checks her work by randomly selecting a day of the week, then reviewing all the items she completed that day. Does the sampling plan result in a random sample? Simple random sample?

Does this sampling plan result in a random sample?
Does this sampling plan result in a simple random sample?

3. Find the mean median mode and midrange for the given sample data in millions of dollars. Given that these the top 10 salaries, do we know anything about the salaries of TV personalities in general? Are such top 10 lists valuable for gaining insight into the larger population?
37.4 36 35.6 26.5 15.3 12.5 12.1 9.2 9.7 8
A. Mean___
B. Median____
C. Mode _____
D. Midrange_____

Given that these are the top 10 salaries, do we know anything about the salaries of TV personalities in general?

Are such top 10 lists valuable for gaining insight into the larger population?

4. A woman wrote to a newspaper advice columnist and claimed that she gave birth 313 days after a visit from her husband, who was in the Navy. Lengths of pregnancies have a mean of 267.6 days and a standard deviation of 15.5 days. Find the z score for 313 days. Is such a length unusual?
The z score is ___
Is the pregnancy length of 313 days unusual?

5. Suppose a baseball player had 208 hits in a season. In the given probability distribution, the random variable X represents the number of hits the player obtained in a game.
x 0 1 2 3 4 5
P(x) 0.1595 0.4758 0.2258 0.0872 0.0449 0.0068
a) Compute and interpret the mean of the random variable X.
µx=____
What is a good interpretation of the mean?
b) Compute the standard deviation of the random variable X.
Ơx=____.

#### Solution Preview

1. Determine whether the description corresponds to an observational study or an experiment.
Forty patients with skin cancer are divided into two groups. One group an experimental drug to fight cancer, the other a placebo. After two years, the spread of the cancer is measured.

Does the description correspond to an observational study or experiment?
Experiment as we are conducting a planed procedure.

2. A worker assembles one item every 20 minutes, so 120 items are completed in her first week of work. Her manager checks her work by randomly selecting a day of the week, then reviewing all the items she completed that day. Does the sampling plan result in a random ...

#### Solution Summary

The solution gives detailed steps on solving some questions on descriptive statistics. All formula and calculations are shown and explained.

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