Suppose your class is investigating the weights of Snickers 1-ounce fun-size can

Question

Suppose your class is investigating the weights of Snickers 1-ounce fun-size candy bars to see if customers are getting full value for their money. Assume that the weights are normally distributed with a population standard deviation = 0.005 ounces. Several candy bars are randomly selected and weighed with sensitive balances borrowed from the physics lab. The weights are: 0.95 1.02 0.98 0.97 1.05 1.01 0.98 1.00 Ounces. We want to determine a 90% confidence interval for the true mean, .

1. What is the sample mean?

2. Explain the meaning of the confidence interval.

3. Determine the z-value. Explain in detail how you knew to use a z-value for this question?

4. Find the margin of error.

5. Determine the 90% confidence interval for the mean weight of the candy bars.

Explanation / Answer

1) sample mean = 7.96/8 = 199/200 = 0.995

2) a range of values so defined that there is a specified probability that the value of a parameter lies within it.

here parameter is population mean

3) z = 1.645

alpha /2 = (1 -0.90 )/2 = 0.05

P(Z >Z*) = 0.05

Z * = 1.645

4) margin of error =z* /sqrt(n) =1.645* 0.005/sqrt(8) = 0.00290797

5)confidence interval

(0.995 - 1.645 *0.0017677)/ , (0.995 + 1.645 *0.0017677)

=(0.99209213,0.997907866)

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