Answer:
The minimum sample size needed is 
. If n is a decimal number, it is rounded up to the next integer. 
is the standard deviation of the population.
Step-by-step explanation:
We have that to find our 
level, that is the subtraction of 1 by the confidence interval divided by 2. So:
Now, we have to find z in the Z-table as such z has a p-value of 
.
That is z with a pvalue of 
, so Z = 1.645.
Now, find the margin of error M as such
In which is the standard deviation of the population and n is the size of the sample.
How large a sample must she select if she desires to be 90% confident that her estimate is within 4 ounces of the true mean?
A sample of n is needed, and n is found when M = 4. So
The minimum sample size needed is . If n is a decimal number, it is rounded up to the next integer. is the standard deviation of the population.
Turn it to improper fractions.
4 1/4 divided by 2/7
Divide them.
17/4 divided by 2/7
17 2 17 x 7
--- ÷ --- = --------- = 119/8 OR 14 7/8
4 7 4 x 2
-----------------------------------------------------
Distribute to take out the parentheses.
(x + 8) - (-3x - 5)
Combine like terms.
x + 8 + 3x + 5
Answer.
4x + 13
Answer: 29 miles per gallon.
Reasoning: 856 miles/29.4 gallons = 29.1156462585 (rounded to the nearest mile = 29)
Hope this helped!
