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Sampling Distribution of Sample Proportion

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1) A store has determined that 25% of all sales are credit sales. A random sample of 75 sales is selected. What is the probability that the sample proportion will be:
a) greater than .34?
b) between .196 and .354?
c) less than .25?
d) less than .10?

2) 10% of items produced by a machine are defective. A random sample of 100 items is selected and checked for defects. What is the probability that the sample will contain:
a) more than .025?
b) less than .13 defective units?

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Solution Summary

The solution provides step by step method for the calculation of probability using z score. Formula for the calculation and shaded graph are also given. Machine defection rates are examined.

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Probability questions/need answers, but explanation of solution
1) A store has determined that 25% of all sales are credit sales. A random sample of 75 sales is selected. What is the probability that the sample proportion will be:
Answers
Let X be the proportion of credit sales. Then X can be assumed to be normal with mean, µ = ...

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