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11 . What is the degrees of freedom ( df ) for this study?

12 . For a two-tailed 95% confidence interval, what is the appropriate t -value to use in the formula?

13 . What is the 95% confidence interval?

14 . What is the 99% confidence interval? Round to two decimal places.

15 . Suppose your sample size had been 30 rather than 20. What would the 95% confidence interval be then? Round to two decimal places

8.3: confidence interval for a population proportion

Use this information to answer the next four exercises. You conduct a poll of 500 randomly selected city residents, asking them if they own an automobile. 280 say they do own an automobile, and 220 say they do not.

16 . Find the sample proportion and sample standard deviation for this data.

17 . What is the 95% two-sided confidence interval? Round to four decimal places.

18 . Calculate the 90% confidence interval. Round to four decimal places.

19 . Calculate the 99% confidence interval. Round to four decimal places.

Use the following information to answer the next three exercises. You are planning to conduct a poll of community members age 65 and older, to determine how many own mobile phones. You want to produce an estimate whose 95% confidence interval will be within four percentage points (plus or minus) the true population proportion. Use an estimated population proportion of 0.5.

20 . What sample size do you need?

21 . Suppose you knew from prior research that the population proportion was 0.6. What sample size would you need?

22 . Suppose you wanted a 95% confidence interval within three percentage points of the population. Assume the population proportion is 0.5. What sample size do you need?

9.1: null and alternate hypotheses

23 . In your state, 58 percent of registered voters in a community are registered as Republicans. You want to conduct a study to see if this also holds up in your community. State the null and alternative hypotheses to test this.

24 . You believe that at least 58 percent of registered voters in a community are registered as Republicans. State the null and alternative hypotheses to test this.

25 . The mean household value in a city is $268,000. You believe that the mean household value in a particular neighborhood is lower than the city average. Write the null and alternative hypotheses to test this.

26 . State the appropriate alternative hypothesis to this null hypothesis: H 0 : μ = 107

27 . State the appropriate alternative hypothesis to this null hypothesis: H 0 : p <0.25

9.2: outcomes and the type i and type ii errors

28 . If you reject H 0 when H 0 is correct, what type of error is this?

29 . If you fail to reject H 0 when H 0 is false, what type of error is this?

30 . What is the relationship between the Type II error and the power of a test?

31 . A new blood test is being developed to screen patients for cancer. Positive results are followed up by a more accurate (and expensive) test. It is assumed that the patient does not have cancer. Describe the null hypothesis, the Type I and Type II errors for this situation, and explain which type of error is more serious.

Questions & Answers

how they find mean population
Joy Reply
parts of statistics
Edwin Reply
what is a mean?
Onele Reply
given the sequence 128,64,32 find the 12th term of the sequence
Shehu Reply
12th number is 0.0625
Thangarajan
why do we use summation notation to represent set of observations
MICHAEL Reply
what is the potential outlier ?
Anik Reply
A pharmaceutical company claims that their pain reliever capsule is 70% effective. But a clinical test on this capsule showed 65 out of 100 effectiveness
jelly Reply
Part of statistics
charls Reply
how to find mean population
Dawit Reply
what is data value
Ravneet Reply
what is relative frequency
Adeyemi Reply
liner regression analysis
Swathy Reply
Proper definition of outlier?
Sumbal Reply
Extraordinary observation (too distant, high, low etc)
Petr Reply
What is outlier?
Sumbal Reply

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Source:  OpenStax, Introductory statistics. OpenStax CNX. May 06, 2016 Download for free at http://legacy.cnx.org/content/col11562/1.18
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