Chapter 7: Q.29 (page 429)
An unknown distribution has a mean of and a standard deviation of six. Let = one object from this distribution. What is the sample size if the standard deviation of is ?
Short Answer
The sample size is.
Chapter 7: Q.29 (page 429)
An unknown distribution has a mean of and a standard deviation of six. Let = one object from this distribution. What is the sample size if the standard deviation of is ?
The sample size is.
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NeverReady batteries has engineered a newer, longer lasting AAA battery. The company claims this battery has an average life span of hours with a standard deviation of hours. Your statistics class questions this claim. As a class, you randomly select batteries and find that the sample mean life span is hours. If the process is working properly, what is the probability of getting a random sample of batteries in which the sample mean lifetime is hours or less? Is the company’s claim reasonable?
The distribution of income in some Third World countries is considered wedge shaped (many very poor people, very few middle income people, and even fewer wealthy people). Suppose we pick a country with a wedge shaped distribution. Let the average salary be per year with a standard deviation of . We randomly survey residents of that country.
a. In words,
b. In words,
c.
d. How is it possible for the standard deviation to be greater than the average?
e. Why is it more likely that the average of the residents will be from to than from ?
A manufacturer produces -pound lifting weights. The lowest actual weight is pounds, and the highest is pounds. Each weight is equally likely so the distribution of weights is uniform. A sample of weights is taken.
Draw the graph from Exercise
Use the information in Example 7.8, but use a sample size of 55 to answer the following questions. a. Find P( x ¯ < 7).
b. Find P(Σx > 170).
c. Find the 80th percentile for the mean of 55 scores.
d. Find the 85th percentile for the sum of 55 scores.
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