Quiz 6 Confidence intervals z Distribution t Distribution.

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Presentation transcript:

Quiz 6 Confidence intervals z Distribution t Distribution

1. What are the z-values for a 90th-percentile confidence interval? b) ±1.645 c) ±1.960 d) ±2.000

2. Calculate the 95th-percentile CI given a sample mean of 110 cm, sample size of 50 and SD of 25.0 cm. a) 85.0 < m < 135.0 cm b) 61.0 < m < 159.0 cm c) 104.2 < m < 115.8 cm d) 103.1 < m < 116.9 cm

3. Determine the t-values for the 95th-percentile confidence interval (CI) given a sample size of n = 12? a) ±2.201 b) ±2.179 c) ±1.960 d) ±1.796

4. Calculate the 95th-percentile CI given a sample mean of 11 4. Calculate the 95th-percentile CI given a sample mean of 11.50 s, sample size of 12 and SD of 2.00 s? a) 9.50 > m > 13.50 s b) 10.92 > m > 12.08 s c) 10.22 > m > 12.77 s d) 10.17 > m > 12.83 s

5. The t-distribution approaches the shape of the standard normal (z) distribution _______? a) as sample size decreases b) as sample standard deviation increases c) as sample size increases d) as sample mean approaches zero

6. What condition is NOT necessary for using the standard normal distribution for computing CIs? a) data are approximately normally distributed b) population SD (s) is known c) sample size greater than 30 d) data are independent

7. Compute the margin of error (E) for a sample size of 20 and a SD of 5.00 for an 80% confidence interval. a) 1.118 b) 1.500 c) 1.328 d) 1.485

8. Estimate the sample size needed to be 80% confident that the population mean is within 25 watts given s = 50.00 W. a) 3 b) 6 c) 7 d) 49