The ________ can be a misleading measure of central tendency if the distribution of scores is ________ . A.mean; B.skewed median
1 answer:
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A set of data has a normal distribution with a mean of 5.1 and a standard deviation of 0.9. Find the percent of data between 4.2 and 5.1.
Answer: The correct option is B) about 34%
Proof:
We have to find
To find , we need to use z score formula:
When x = 4.2, we have:
When x = 5.1, we have:
Therefore, we have to find
Using the standard normal table, we have:
=
or 34.13%
= 34% approximately
Therefore, the percent of data between 4.2 and 5.1 is about 34%
Answer:
We need a sample size of at least 75.
Step-by-step explanation:
We have that to find our level, that is the subtraction of 1 by the confidence interval divided by 2. So:
Now, we have to find z in the Ztable as such z has a pvalue of .
So it is z with a pvalue of , so
Now, we find the margin of error M as such
In which is the standard deviation of the population and n is the size of the sample.
The standard deviation is the square root of the variance. So:
With a .95 probability, the sample size that needs to be taken if the desired margin of error is 5 or less is
We need a sample size of at least n, in which n is found when M = 5. So
We need a sample size of at least 75.