# Statistics

posted by .

The Wechsler Adult Intelligence Scale (WAIS) is a common "IQ test" for adults. The distribution of WAIS scores for persons over 16 yrs of age is approximately Normal with mean (100) and Standard Deviation 15,

(a) Whatis the probability that a random chosen individual has a WAIS score of 105 or higher?

(b) What are the mean and standard deviation of the average WAIS score of x for a SRS of 60 people?

(C) What is the Probability that the average WAIS score of an SRS of 60 people is 105 or higher?

Use z-scores and the normal distribution table for these problems.

For example:
a) Use z-score formula: z = (x - mean)/sd

z = (105 - 100)/15 = 0.33

Look at a normal distribution table using z = 0.33 and determine the area under the curve that would represent this z-score and higher (upper tail of the distribution curve). That would then be your probability.

If a sample size is given, that needs to be computed into the formula:
z = (x - mean)/(sd/sqrt of sample size)
Note: sqrt = square root.

I hope this will get you started.

## Similar Questions

1. ### statistics

Scores on a test have a mean of 66 and Q3 of 81. The scores have a distribution that is approximately normal. Find the standard deviation. Round your answer to the nearest tenth.
2. ### Statistics

1. Which of the following statements are correct?
3. ### statistics

The Intelligence Quotient (IQ) test scores for adults are normally distributed with a mean of 100 and a standard deviation of 15. What is the probability we could select a sample of 50 adults and find the mean of this sample is between …
4. ### statistics

It is known that the population mean for the Full Scale IQ of the WAIS is 100 with a standard deviation of 15. A researcher assesses a sample of 200 adults and find that they have a mean Full Scale IQ of 102. The point estimate of …
5. ### statistics

It is known that the population mean for the Full Scale IQ of the WAIS is 100 with a standard deviation of 15. A researcher assesses a sample of 200 adults and find that they have a mean Full Scale IQ of 102. The point estimate of …
6. ### statistics

It is known that the population mean for the Full Scale IQ of the WAIS is 100 with a standard deviation of 15. A researcher assesses a sample of 200 adults and find that they have a mean Full Scale IQ of 102. The point estimate of …
7. ### statistics

It is known that the population mean for the Full Scale IQ of the WAIS is 100 with a standard deviation of 15. A researcher assesses a sample of 200 adults and find that they have a mean Full Scale IQ of 102. The point estimate of …
8. ### Statistics

The distribution of IQ scores is a nonstandard normal distribution with a mean of 100 and a standard deviation of 15. What are the value of the mean and standard deviation after all IQ score have been standardized by converting them …
9. ### statistics/normal distribution

Find the area of the shaded region.The graph to the right depicts IQ scores of Adults (85-120), and those scores are normally distributed with a mean of 100 and a standard deviation of 15
10. ### Elementary Statistics

"Scores on the Wechsler IQ test approximate a normal curve with a mean of 100 and a standard deviation of 15. b. What percentage of IQ scores are below 74?

More Similar Questions