1.A random sample of size 70 has a standard deviation of 15. What is the margin of error for a 92% confidence level?

2.Compute the length of the confidence interval for estimating the population mean using a sample size of 300 and with a standard deviation 84. Use a 92% confidence level.

3.A random sample size of 70 was used with a population standard deviation of 15. Assuming that there is a 92% confidence level, what is the margin of error?

4.Compute for the appropriate sample size needed if the margin of error is 15, with a population standard deviation of 43 and a 98% level of confidence.

5.A researcher found that the IQ scores of the ALS students in the Division of Quezon Province are normally distributed with a mean of 110 and a standard deviation of 10.

a.How many ALS students are needed to test so that the estimate will not be more than 5 from the population mean with a 99% level of confidence?

b.Due to limited contact with ALS students, the researcher tested a small number of ALS students. Explain the effect of this small sample on the estimate of the parameter?

6.A confidence interval estimate has a maximum error of 2.50. If the distribution of the data where the estimate is obtained is normal with a standard deviation of 9.

a.How many samples are considered in 98% confidence interval estimate for the mean?

b.What must be done to the sample size to reduce the margin of error of the confident interval estimate? Support your answer.

1.Find the values of t for which the area on the right tail of the t-distribution is 0.05 and the number of degrees of freedom is equal to:

a.15

b.28

c.100

2.Find the 99th percentile of the t-distribution with 18 degrees of freedom.

3.Find the 90th percentile of the t-distribution if the sample size is 25.

Write "REAL" if the statement is true about the t-distribution and "FAKE" if it's not.

_________1. The t-distribution is used to estimate population parameters when the sample size is small and/or the population variance is unknown.

_________2. The mean, median and mode are all equal to zero.

_________3. The variance is equal to 1.

_________4. The t-distribution curve is bell-shaped.

_________5. The standard deviation is always greater than 1.

_________6. Half of the total area under the t-distribution curve is equal to 1.

_________7. The curve is symmetrical about its zero.

_________8. The shape of the t-distribution curve depends on the sample mean.

_________9. The tails of the t-distribution curve approach the horizontal axis but never touch it.

_________10. As the degrees of freedom increase, the t-distribution curve looks more and more like the normal distribution.