# Chapter 1. Large-Sample Confidence Intervals for Proportions

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Stat Tutor
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1:46

### Question 1.1

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Incorrect. We use sample proportion, $$\widehat{p}$$, to estimate the population proportion, p.
Correct. We use sample proportion, $$\widehat{p}$$, to estimate the population proportion, p.
Incorrect. Try again.
2

2:19

### Question 1.2

Phj/BDnFX5QKBrfOuCeGilICqwao59BrwjO8K4qzh77mZC9mQSYiwiRJh4bu5NtnTurqsZbR1zkA/kRx7Qz8ZKwRnseJTitQFwmWXRpZKy4YO+kPPikMw9RiGAyF5YEBe3kwkvvEcXTFvv6RqfepK9MKUlQGsWDikD9VFYmUckc+jye4dm1JyAyQqwVPiYe8WXbTpYnH+vdcmDyiKiyCrqkD5kOQOj7req3iz7nBxQQUpRDXkYL0dsOPKlR+nOkEtyg/r1L7KFJh0JMwyvxXuvqVVf9SMrAEe5tBz9/tHUdE+Mr1PedpSvouX59QBEwbm1ddaiOO3nHTjuK/JiNW21Q3gJvyRPeo72Pm1qNhqoLTEd1yGz+Eo1fW6tb2olNovLJYmcdqTrS9W27kgd1dDAh+JY1qYWpPElU8pLblwpmZVsOYL5MjDFbprAHWNoXubYWHMzHPt9GAazliOJjdd+684wsKdFXK
Incorrect. We check $$n \widehat{p} \geq 15$$ and $$n(1- \widehat{p} ) \geq 15$$; we cannot check $$np \geq 10$$ and $$n(1-p) \geq 10$$ because we don't know the value of p.
Correct. We check $$n \widehat{p} \geq 15$$ and $$n(1- \widehat{p} ) \geq 15$$; we cannot check $$np \geq 10$$ and $$n(1-p) \geq 10$$ because we don't know the value of p.
Incorrect. Try again.
2

2:52

### Question 1.3

vNEYyOsRLdnih2i4KplDotVkGU3J20slNnaHz9j7y/1b9k5EaUccZ0m6oVMKtBIUeeE0TNgqpxhftcBAj00RdaZBVCCb6eHWplx4nYLWHTIMao56WOfl701Kufhj6Xzhxg3ChAcbjP3IXrlOEOMKVjr8Y0HhgBMMKz9WtMpWOxFfs9Nxj2yHWCSTto+iwRfevbz1bm2sn5c8DfB9vypOQXkXvU9Qf1yes9VYbksNLsE6UT4q9ktWYIsMCY8GGASVRNDkkmj9GTC7EhyLng4I6dZr2TEoI7SqonouYJg+AZQepDvC65XP9kpHpY6JiGrflLnenw==
Incorrect. Margin of error for estimating p is $$z \sqrt{ \frac{ \widehat{p}(1- \widehat{p}) }{n} }$$.
Correct. Margin of error for estimating p is $$z \sqrt{ \frac{ \widehat{p}(1- \widehat{p}) }{n} }$$
Incorrect. Try again.
2

4:08

### Question 1.4

iGvhoQxkM2dNQ9E2Fp6wUC975EHXN6CtyL3AGfqnuqIDZIhUVXRNEaU/Wj83o+plvTLWxN2CLwBQ/c4lmvkImqXN/vVJV4/LHkBfFwwBJNMH6UShybLv82c7vhBHFJmAY7XJA2krqxFmJc2KNPDxQf3abKOiKPwaXA5D5ZtIYv7aypJorQCfVXZOmWqwi4IRCWq/5/xUVkkiyDI9UyfafnfRtKGJG/WUsTui13nwNyQIgkbgUnmRq6MkYvBaj74bxB4S4amk229m0Zng
Incorrect. Data should be collected with a simple random sample.
Correct. Data should be collected with a simple random sample.
Incorrect. Try again.
2

5:16

### Question 1.5

Incorrect. The parameter to be estimated is the proportion of all Americans who approve of President Obama's job as president.
Correct. The parameter to be estimated is the proportion of all Americans who approve of President Obama's job as president.
Incorrect. Try again.
2

7:17

### Question 1.6

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
Incorrect. 0.46 is a value of $$\widehat{p}$$; it is the proportion who approve of President Obama's job as president in the sample of 1544 Americans.
Correct. 0.46 is a value of $$\widehat{p}$$; it is the proportion who approve of President Obama's job as president in the sample of 1544 Americans.
Incorrect. Try again.
2

8:23

### Question 1.7

7ViZFsOoE/tkmjWfPjYwvV6T54IT43JOFVNP2LnmCLHKTauTOAO+w8bCk6gt8GnZyxS/w0rN5do6gShHMR+BIm6CF07tuDKoWKgglmAhVTIONz6wocpPgGP7LwktRjhYS/0UCIEh0Vv38EQFT7iKXJx9CbDplHSUBxicR6czVn95YhUUf086eeOOzAXvAjmjVLi0yPUqpCwLhbycWCG6Yw==
Incorrect. $$z \sqrt{ \frac{ \widehat{p}(1- \widehat{p}) }{n} }$$ = $$1.96 \sqrt{ \frac{0.46(1-0.46)}{1544} } = 0.025$$ is the margin of error for estimating $$\widehat{p}$$.
Correct. $$z \sqrt{ \frac{ \widehat{p}(1- \widehat{p}) }{n} }$$ = $$1.96 \sqrt{ \frac{0.46(1-0.46)}{1544} } = 0.025$$ is the margin of error for estimating $$\widehat{p}$$.
Incorrect. Try again.
2

9:03

### Question 1.8

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Incorrect. It is usually 95%.
Correct. It is usually 95%.
Incorrect. Try again.
2

9:09

### Question 1.9

Incorrect. 0.67 is a value of $$\widehat{p}$$; it estimate the proportion of all adults in the United States who drink alcohol.
Correct. 0.67 is a value of $$\widehat{p}$$; it estimate the proportion of all adults in the United States who drink alcohol.
Incorrect. Try again.
2

### Question 1.10

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Incorrect. Gallup reported, "For results based on a sample of 1,020 national adults, one can say with 95% confidence that the maximum margin of sampling error is ±3 percentage points."
Correct. Gallup reported, "For results based on a sample of 1,020 national adults, one can say with 95% confidence that the maximum margin of sampling error is ±3 percentage points."
Incorrect. Try again.
2

12:06

### Question 1.11

2hxoqKH3PrQryX3+iPyklLRh9JaNPlfH4XnTdsE6wrwaBTxzEpxYVrytNGeKU9ICa70qCVcYKe4wF8NA+lIIqSIWcUT2fcLz6BLHOn45j8PuzjVbMCfkpCcOQwfoQrtbqvFsLm+++lHi+fhbk4tuQp177J8nw/gG6K05rk87EjnTZKWYaRm0FpT0xYmx4U30Ghfm1pJ2/zD2k7lW
Incorrect. Both are the same: 0.03 or 3%.
Correct. Both are the same: 0.03 or 3%.
Incorrect. Try again.
2

### Question 1.12

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Incorrect.
Correct.
Incorrect. Try again.
2