Question

PLEASE!!!

A survey asks a random sample of 2500 adults in Ohio if they support an increase in the state sales tax from 5.25% to 5.50%, with the additional revenue going to education. Let X denote the number in the sample that say they support the increase. Suppose that 30% of all adults in Ohio support the increase.

9. The standard deviation of X is

a. 22.91.

b. 27.39.

c. 5255.

d. 750.


10. The probability that X is at least 800 is

a. less than 0.0001.

b. about 0.015.

c. 0.025.

d. 0.05.

Answer 1

Explanation:

a) Total number of people surveyed, n = 2500

Let X denote the number in the sample that say they support the increase. If 30% of all adults in Ohio support the increase, it means that the percentage of all adults in Ohio that did not support the increase is

100 - 30 = 70%

This is a binomial probability because there are only two possible outcomes. Therefore,

Probability of success, p = 30/100 = 0.3

Probability of failure, q = 1 - p = 1 - 0.3

q = 0.7

Standard deviation = √npq

Standard deviation = √(2500 × 0.3 × 0.7) = 22.91

b) The probability that x is at least 800 is expressed as

P(x ≥ 800)

We would determine the probability by using the binomial probability calculator. Therefore,

P(x ≥ 800) = 0.01577

b. about 0.015.