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Gravity
Terms in this set (20)
The probability of making a Type I error when the null hypothesis is true as an equality is called the
level of significance.
Whenever the probability of making a Type II error has not been determined and controlled, only two conclusions are possible. We either reject H0 or
do not reject H0 .
We can reduce the margin of error in an interval estimate of p by doing any of the following except
increasing the planning value p* to 0.5.
Which of the following describe a Type II Error?
Accept H0 when H0 is false.
The p-value is a probability that measures the support (or lack of support) for the
null hypothesis
The average gasoline price of one of the major oil companies has been hovering around $2.20 per gallon. Because of cost reduction measures, it is announced that there will be a significant reduction in the average price over the next month. In order to test this belief, we wait one month, then randomly select a sample of 36 of the company's gas stations. We find that the average price for the stations in the sample was $2.15. The standard deviation of the prices for the selected gas stations is $0.10. Determine the test statistic.
t=(2.15-2.20)/(.1/sqrt(36))
Which of the following null hypotheses cannot be correct?
The null hypothesis always has to contain a statement of equality, therefore cannot be correct.
H0 u not equal to 10
For the interval estimation of μ when σ is known and the sample is large, the proper distribution to use is
the normal distribution.
Which of the following describe a Type I Error?
Reject H0 when H0 is true.
A researcher is interested in determining the average age at which people obtain their first credit card. If past information shows a mean of 22 years and a standard deviation of 2 years, what size sample should be taken so that at 95% confidence the margin of error will be 3 months or less?
246
A student wants to determine if pennies are really fair, meaning equally likely to land heads up or tails up. He flips a random sample of 50 pennies and finds that 28 of them land heads up. What is the value of the test statistic?
z = 0.85
A statistics teacher started class one day by drawing the names of 10 students out of a hat and asked them to do as many pushups as they could. The 10 randomly selected students averaged 15 pushups per person with a standard deviation of 9 pushups. Suppose the distribution of the population of number of pushups that can be done is approximately normal. Which of the following statements is true?
A t distribution should be used because σ is unknown.
The CEO of a company wants to estimate the percent of employees that use company computers to go on Facebook during work hours with 95% confidence. He selects a random sample of 150 of the employees and finds that 53 of them logged onto Facebook that day. The CEO would like to cut the margin of error in half without changing the confidence level. How large of a sample size is needed?
600
The manager of a grocery store has taken a random sample of 100 customers. The average length of time it took these 100 customers to check out was 3 minutes. It is known that the standard deviation of the population of checkout times is 1 minute. With a 0.95 probability, the sample mean will provide a margin of error of 0.196. If we wanted to cut this margin of error in half, how many customers would we need to include in our sample?
400
Using an α = 0.04 a confidence interval for a population proportion is determined to be 0.65 to 0.75. If the level of significance is decreased, the interval for the population proportion
becomes wider
A poll of 600 voters showed 210 that were in favor of stricter gun control measures. Develop a 90% confidence interval estimate for the proportion of all the voters who are in favor of stricter gun control measures.
0.32 to 0.38
In general, higher confidence levels provide larger confidence intervals. One way to have high confidence and a small margin of error is to
increase the sample size
A local health center noted that in a sample of 400 patients 80 were referred to them by the local hospital. What size sample would be required to estimate the proportion of hospital referrals with a margin of error of 0.04 or less at 95% confidence?
385
Sales data from a family-owned store shows that 78% of a random sample of 300 customers pay using a credit card. Compute the 99% confidence interval for the population proportion.
0.71 to 0.84
A statistics teacher started class one day by drawing the names of 10 students out of a hat and asked them to do as many pushups as they could. The 10 randomly selected students averaged 15 pushups per person with a standard deviation of 9 pushups. Suppose the distribution of the population of number of pushups that can be done is approximately normal. What is the standard error of the mean?
2.876xd
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