QUESTION FIVE The diameter of shafts produced in a machine follows a normal distribution with the...

QUESTION FIVE

The diameter of shafts produced in a machine follows a normal distribution with the variance of 81mm. A random sample of 36 shafts taken from the production has its mean diameter of 30mm. Find a 95% confidence interval for the diameter of shafts.

The Marketing manager of a company feels that 42% of retailers will have enhanced weekly sales after introducing an advertisement at the point of sales. A sample of 36 retailers shops of the company, where the point of sales advertisement has been displayed, reveals that only 18 of them are having enhanced sales after displaying the advertisement. Find the 95% confidence interval for the proportion representing the enhanced sales.

c. The Finance manager of a company feels that 55% of branches will have enhanced yearly collection of deposits after introducing a hike in interest rate. Determine the sample size such that the mean proportion is with plus or minus 0.05 confidence level of 90%?

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milcah answered 8 months ago

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