Joel is constructing a line perpendicular . He has already constructed three arcs as shown. Use the image to answer the question
. He moves his compass point to W to construct a fourth arc.
What must be true about the width of Joel’s compass opening before he draws the arc?
It must be narrower than it was when constructing the arc above P.
It must be the same as it was when constructing the arc above P.
It must be wider than it was when constructing the arc above P.
What must be true about the width of Joel’s compass opening before he draws the arc?
It must be narrower than it was when constructing the arc above P.
It must be the same as it was when constructing the arc above P.
It must be wider than it was when constructing the arc above P.
2 answers:
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Answer:
a) The mean is 18 and the standard deviation is 1.79.
b) The interpretation is that the standard deviation of the sample means of groups of 20 students will be of 1.79, which is the sample error, which is different from the population standard deviation.
c) 0.2005 = 20.05% probability that a sample of 20 students has a mean score of 19.5 or more.
Step-by-step explanation:
To solve this question, we need to understand the normal probability distribution and the central limit theorem.
Normal Probability Distribution:
Problems of normal distributions can be solved using the z-score formula.
In a set with mean and standard deviation
, the z-score of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
Central Limit Theorem
The Central Limit Theorem estabilishes that, for a normally distributed random variable X, with mean and standard deviation
, the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean
and standard deviation
.
For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.
Mean of 18 and a standard deviation of 8.
This means that
Sample of 20:
This means that
(a) Calculate the mean and standard deviation of the sampling distribution of x¯.
By the Central Limit Theorem, the mean is 18 and the standard deviation is 1.79.
(b) Interpret the standard deviation from part (a).
The interpretation is that the standard deviation of the sample means of groups of 20 students will be of 1.79, which is the sample error, which is different from the population standard deviation.
(c) Find the probability that a sample of 20 students has a mean score of 19.5 or more.
This is 1 subtracted by the pvalue of Z when X = 19.5. So
By the Central Limit Theorem
has a pvalue of 0.7995
1 - 0.7995 = 0.2005
0.2005 = 20.05% probability that a sample of 20 students has a mean score of 19.5 or more.