A random sample of 42 textbooks has a mean price of $114.50 and a standard devia

Question

A random sample of 42 textbooks has a mean price of $114.50 and a standard deviation of $12.30. Find a point estimate for the mean price of all textbooks. $42 $12.30 $114.50 $2.73 None Find the critical value z_c necessary to form a 98% confidence interval. 2.33 2.05 0.5040 0.8365 None A random sample of 42 textbooks has a mean price of $114.50 and a standard deviation of $12.30. Find a 98% confidence interval for the mean price of all textbooks. (111.38,117.62) (110.08,118.92) (110.78,118.22) (109.61,119.39) None Determine the minimum sample size needed to construct a 95% confidence interval for the mean age of employees at a company. The estimate must be accurate to within 0.5 year. Assume the standard deviation is 4.8 years. 18 B. 19 354 355 None

Explanation / Answer

5.

A random sample of 42 textbooks has a mean price of $114.50 and a standard deviation of $12.30. Find a point estimate for the mean price of all textbooks

(ANS) A point estimate for the mean price of all textbooks is $114.50

6.

Find the critical value z c necessary to form a 98% confidence interval

(ANS) Here C=0.98 so the area in each tail is

               1/2(1-C)

              1/2(1-0.98)

              0.01

The area to the left of Zc is 0.98+0.01=0.99

using Excel, NORMSINV(0.99) = 2.33

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