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vovikov84 [41]
3 years ago
9

Two Physics classes at Jefferson High School took the same quiz. Mr. Spears had 20 students in his class with a mean score of 80

. Mrs. Guyton's class of 30 students had a mean score of 90. Overall, what was the mean score for all students on the quiz
Mathematics
1 answer:
andriy [413]3 years ago
4 0

Answer:

The mean score for all students on the quiz was 86.

Step-by-step explanation:

This question is solved by a weighed average.

To find the weighed average, we add the values multiplied by their weight, and after that we divide by the sum of weights.

In this problem, we have that:

Mr. Spears had 20 students in his class with a mean score of 80.

So 80 has a weight of 20.

Mrs. Guyton's class of 30 students had a mean score of 90.

So 90 has a weight of 30.

Overall, what was the mean score for all students on the quiz

M = \frac{80*20 + 90*30}{20 + 30} = 86

The mean score for all students on the quiz was 86.

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Answer:

Confidence interval variance [21.297 ; 64.493]

Confidence interval standard deviation;

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Step-by-step explanation:

Given :

Variance, s² = 34.34

Standard deviation, s = 5.86

Sample size, n = 27

Degree of freedom, df = 27 - 1 = 26

Using the relation for the confidence interval :

[s²(n - 1) / X²α/2, n-1] ; [s²(n - 1) / X²1-α/2, n-1]

From the chi distribition table :

X²α/2, n-1 = 41.923 ; X²1-α/2, n-1 = 13.844

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The 95% confidence interval for the population variance is :

21.297 < σ² < 64.493

Standard deviation is the square root of variance, hence,

The 95% confidence interval for the population standard deviation is :

4.615 < σ < 8.031

3 0
2 years ago
Click on the correct answer.
Galina-37 [17]

Answer:

A, $1.08

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1.20 / 90 = 1.08

use a calculator

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