How large a sample should be selected to provide a 95 confidence interval with a margin of error of 10? Assume that the population standard deviation is 40.

the required sample size is 62

Step-by-step explanation:

Given the data in the question;

Confidence interval C = 95% = 0.95

Margin of error E = 10

population standard deviation σ = 40

sample size n = ?

We use the following formula to get our sample size;

sample size n = ( ( × σ ) / E )²

Next we find z value for confidence interval

Confidence interval C = 95% = 0.95

Area = ( 1 + c )/2 = ( 1 + 0.95)/2 = 1.95 / 2 = 0.975

Now we check our z-table to see the area where 0.975 falls;

It falls under column 0.06 and Row 1.9

so, our z-value for confidence interval of 0.95 is 1.96

so we substitute

sample size n = ( ( 1.96 × 40 ) / 10 )²

n = ( 78.4 / 10 )²

n = ( 7.84 )²

n = 61.4656

we know that sample size is always rounded up, so

n = 62

Therefore, the required sample size is 62

to find the unit price of an object, you divide the price by object. you are trying to find out how much an object cost per unit.

for instance, lets say you have 50lb of ice cream(object) that cost 8.00 dollars(price). to find the unit cost, we take the 8.00 and divide it by 50, which will give us .16 cents per pound. we can check this by multiplying .16 by 50 = 8.00

so

object = e2

price = d2

unit price = c2

formula for c2:

=d2 / e2

so in my example about ice cream, we would have the following.

e2 = 50

d2 = 8.00

c2 formula:

=d2 / e2