test 1 anwers for midterm

Suppose a random variable X is best described by normal distribution with mean=81 and the standard deviation=9. Find the Z score that corresponds with the value X=90

1

And a hypothesis testing involving a population mean, which of the following would be acceptable formulation?

H0: μ= $1700 Ha: μ ≠ $1700

researchers have claimed that an average number of headaches per student during a semester of stats is 11. Statistics students believe the average is higher.. in a sample of n=23 students the mean is 17 headaches with a deviation of 1.8. Which of the following represents the normal and alternative hypotheses necessary to test the students beliefs?

H0: μ= 11 Ha: μ > 11

suppose a 95% confidence level for μ(mean), turns out to be (1,000 to 2,100). To make more useful inferences from the data, it is desired to reduce the width of the confidence level. Which of the following will result a reduced interval width?

Increase the sample size

You have created a 90% confidence interval with a mean with the result 105 ≤ μ ≤ 109. What decision will you make if we test?:H0: μ= 110 H1: μ≠ 110 and a=0.10

Reject H0 in favor of Ha

in a metal fabrication process, metal rods are produced to a specificied target length of 15 feet. Suppose that the lengths are normally distributed a quality control specialist collects a random sample of 16 rods and finds a sample main length to be 14.8 feet. And a standard deviation of 0.65 feet. Which of the following statements is true?

The sampling distribution for the sample main follows the T distribution with 15 degrees of freedom

state, the proper conclusion of the test had an hypothesis value at 0.50 .

This is sufficient evidence to indicate the true proportion of college students who prefer the brand of soda differs from 0.50

The sampling distribution of any mean becomes normal as the sample size grows. This is true, regardless the population distribution. However, if the population distribution is very skewed, it may take a sample size of dozens or even hundreds of observations for the normal model to work well.

True

When conducting a hypothesis test of a proportion or mean, the construct of your alternative hypothesis determined whether it is a one or two tail test

True

the probability that a Standard normal variable, Z, is between -1.10 and -2.10 is the same as the probability Z between +2.10 and +1.10

True

A manufacturer of cream filled donuts collected data from its automatic filling process, the amount of cream inserted into the donut is normally distributed. To make sure that the automatic filling process is on target, quality control, inspectors take a sample of 25 donuts and measure the weight of cream filling. They find the 99% confidence interval of 14.16 215.84 grams. Which of the following is the correct interpretation?

We are 99% confident that the true weight of cream filling in all donuts made by this process is between 14.16 and 15.84 grams.

if a hypothesis test is conducted for a population me, a null and alternative hypothesis of the form: H0: μ= 1000 Ha: μ ≠ 1000 will result in a one tail hypothesis test since the sample result can fall in only one tail

false

In its standardized form, the normal distribution

has a mean of 0 and a standard deviation of 1

A two tailed hypothesis test of a mean with a(alpha)=0.10 is similare to a 90 percent confidence level

true

if the mean is greater than the median than the data is right skewed

true