A preliminary sample of holiday shoppers revealed that the standard deviation of the amount of money they are planning to spend on gifts during the coming holiday season is $80. How many holiday shoppers should be sampled in order to estimate the average amount of money spent on gifts by all holiday shoppers with a margin of error of $7 and with a 99% confidence

So the answer for this case would be n=870 rounded up to the nearest integer

Step-by-step explanation:

Information given

represent the deviation

ME = 7 represent the margin of error

Solution

The margin of error is given by this formula:

   (a)

And on this case we have that ME =7 and we are interested in order to find the value of n, if we solve n from equation (a) we got:

  (b)

The critical value for 99% of confidence interval now can be founded using the normal distribution. The significance level would be and . The critical value would be , replacing into formula (b) we got:

So the answer for this case would be n=870 rounded up to the nearest integer

they are simplified

step-by-step explanation:

c.

step-by-step explanation:

she should of added 9^2 and 12^2. that is because it is a^2+b^2=c^2. c^2 is the hypotenuse and should always be bigger than the other two numbers. which is why she should of added 9 squared and 12 squared together instead of 15 squared.