the average price of regular unleaded gas in a large city is approximately norma

Question

the average price of regular unleaded gas in a large city is approximately normal with mean of #3.45 and the standard deviation of $.24. suppose a random sample of 16 gas stations in the city are selected. the average of this sample is $3.56. suppose another randome sample of 16 stations yelied a sample mean of $.3.42

1.) what is the chance the average unleaded gas price for a randomly selected sample of 16b is greated than $3.50

2.) suppose from each one of the sample we calculate 90% confidence interval... which statement is false

a. one in every ten second will not contain the true mean

b. all intervall will all be centered at $3.45

c. the margin of error is the same for every interval

d. 90% of all possible intervall will contain the population mean

Explanation / Answer

1) Z = (x-mean)/ sigma/sqrt(n) = (3.50-3.42)/[0.24/sqrt(16)]= 1.333

P(z > 1.333) = 0.091217 from the normal tables.

2) The confidence intervals are centered at sample mean and not the population mean. Hence, B is false statement.

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