Amarketing specialist wants to estimate the average amount spent by visitors to an online retailer's newly-designed website. from the data in a preliminary study she guesses that the standard deviation of the amount spent is about 12 dollars.

how large a sample should she take to estimate the mean amount spent to within 4 dollars with 98% confidence? (round your answer up to the next largest integer).

n=49

Step-by-step explanation:

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

Assuming the X follows a normal distribution

We know that the margin of error for a confidence interval is given by:

  (1)

The next step would be find the value of , and

Using the normal standard table, excel or a calculator we see that:

If we solve for n from formula (1) we got:

And we have everything to replace into the formula:

And if we round up the answer we see that the value of n to ensure the margin of error required dollars is n=49.

the balance is found at the link

step-by-step explanation:

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