An analyst from an energy research institute in California wishes to precisely e

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An analyst from an energy research institute in California wishes to precisely estimate the (1-)100% ( shown on right) confidence interval for the average price of unleaded gasoline in the state. In particular, she does not want the sample mean to deviate from the population mean by more than + B dollars. What is the minimum number of gas stations that she should include in her sample if she uses the standard deviation estimate of s dollara, as reported in the popular press?ROUND THE t or Z STATISTIC OFF TO 2 DECIMAL PLACES [1.645 rounds off to 1.64]. B = 0.04 s = 0.22 = 0.01 a. 164 b. 15 c. 30 d. 202 e. none An analyst from an energy research institute in California wishes to precisely estimate the (1-)100% ( shown on right) confidence interval for the average price of unleaded gasoline in the state. In particular, she does not want the sample mean to deviate from the population mean by more than + B dollars. What is the minimum number of gas stations that she should include in her sample if she uses the standard deviation estimate of s dollara, as reported in the popular press?ROUND THE t or Z STATISTIC OFF TO 2 DECIMAL PLACES [1.645 rounds off to 1.64]. B = 0.04 s = 0.22 = 0.01 a. 164 b. 15 c. 30 d. 202 e. none

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Answer:

An analyst from an energy research institute in California wishes to precisely estimate the (1-)100% ( shown on right) confidence interval for the average price of unleaded gasoline in the state. In particular, she does not want the sample mean to deviate from the population mean by more than + B dollars. What is the minimum number of gas stations that she should include in her sample if she uses the standard deviation estimate of s dollara, as reported in the popular press?ROUND THE t or Z STATISTIC OFF TO 2 DECIMAL PLACES [1.645 rounds off to 1.64].

For 99%, z=2.58

d=0.04

sd=0.22

Sample size = (z2*s2)/d2

= (2.582*0.222)/0.042

=201.356

The sample size required= 202.

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