# statistics

posted by .

A school psychologist is trying to determine the lower boundary of a confidence interval for a IQ measure that has a mean of 100 and a standard deviation of 30 and a sample size of 100. What is the lower boundary if she was to create a 95% confidence interval?

• statistics -

CI95 = mean + or - 1.96(sd/√n)
...where + or - 1.96 represents the 95% confidence interval using a z-table, sd = standard deviation, √ = square root, and n = sample size.

CI95 = 100 + or - 1.96(30/√100)

I'll let you take it from here.

## Similar Questions

1. ### Statistics

It is known that the amount of time needed to change the oil in a car is normally distributed with a standard deviation of 5 minutes. A random sample of 100 oil changes yielded a sample mean of 22 minutes. Compute the 99% confidence …
2. ### statistics

what are the mean and standard deviation of a sampling distribution consisting of samples of size 16?
3. ### Statistics

A 82% confidence interval for a sampling distribution with a mean of 100, a sample standard deviation of 24 and a sample size of 36 will be based on a á= ______ and a corresponding Zá of ___
4. ### Statistics

A 82% confidence interval for a sampling distribution with a mean of 100, a sample standard deviation of 24 and a sample size of 36 will be based on a á= ______ and a corresponding Zá of ___
5. ### statistics

a sample of 100 persons had a mean of 80 for a measure and the population standard deviation of 5. what ia the 99% confidence interval for the mean?
6. ### statistikc

We want a confidence interval for the mean IQ of all the 7th grade girls in that school district. We do not know the population standard deviation so we use the confidence interval that uses the t. In order to use the t-interval we …
7. ### Statistics

An IQ test is designed so that the mean is 100 and the standard deviation is 19 for the population of normal adults. Find the sample size necessary to estimate the mean IQ score of statistics students such that it can be said with …
8. ### statistics

An IQ is designed so that the mean is 100 and the standard deviation is 23 for the population of Normal adults, find the sample size necessary to estimate the mean IQ score of statistics students Such that it can be said with 90% confidence …
9. ### Statistics

Find the margin of error for a 95% confidence interval for estimating the population mean when the sample standard deviation equals 100, with a sample size of (i) 400, (ii) 1600. What is the effect of the sample size?
10. ### Statistics

Find the margin of error for a 95% confidence interval for estimating the population mean when the sample standard deviation equals 100, with a sample size of (i) 400, (ii) 1600. What is the effect of the sample size?

More Similar Questions