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Westkost [7]
3 years ago
10

A group of researchers conducted a study to determine whether the final grade in an honors section of introductory psychology wa

s related to a student’s performance on a test of math ability administered for college entrance. The researchers looked at the test scores of 200 students (n= 200) and found a correlation of r= .45 between math ability scores and final course grade. The proportion of the variability seen in final grade performance that can be predicted by math ability scores is ____.
Mathematics
1 answer:
pishuonlain [190]3 years ago
4 0

Answer:

r=\frac{n(\sum xy)-(\sum x)(\sum y)}{\sqrt{[n\sum x^2 -(\sum x)^2][n\sum y^2 -(\sum y)^2]}}

And for this case r =0.45

The % of variation is given by the determination coefficient given by r^2 and on this case 0.45^2 =0.2025, so then the % of variation explained is 20.25%.

The proportion of the variability seen in final grade performance that can be predicted by math ability scores is 20.25%.

Step-by-step explanation:

For this case we asume that we fit a linear model:

y = mx+b

Where y represent the final grade and x the math ability scores

m=\frac{S_{xy}}{S_{xx}}  

Where:  

S_{xy}=\sum_{i=1}^n x_i y_i -\frac{(\sum_{i=1}^n x_i)(\sum_{i=1}^n y_i)}{n}  

S_{xx}=\sum_{i=1}^n x^2_i -\frac{(\sum_{i=1}^n x_i)^2}{n}  

\bar x= \frac{\sum x_i}{n}  

\bar y= \frac{\sum y_i}{n}  

And we can find the intercept using this:  

b=\bar y -m \bar x  

The correlation coeffcient is given by:

r=\frac{n(\sum xy)-(\sum x)(\sum y)}{\sqrt{[n\sum x^2 -(\sum x)^2][n\sum y^2 -(\sum y)^2]}}

And for this case r =0.45

The % of variation is given by the determination coefficient given by r^2 and on this case 0.45^2 =0.2025, so then the % of variation explained is 20.25%.

The proportion of the variability seen in final grade performance that can be predicted by math ability scores is 20.25%.

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