Practice problem 3: A statistics professor has misplaced your final exam. The pr

Question

Practice problem 3: A statistics professor has misplaced your final exam. The professor is not worried about it because she feels she can make a very good prediction of what your final exam grade would be. She takes all the midterm grades (except yours) of the students and calls them x. She then takes all the final exam es and calls them y. She makes a scatter graph that is linear and calculates which is .70. She then finds the best fit equation and uses it to predict your final exam grade based on the fact she knows your midterm grade. You feel this is unfair From a statistical point of view how would you argue that she shouldn't do this? (Hint: Calculate r-squared (square the r value given) and use this in your argument). 1. UNDERSTAND. 2. TRANSLATE. 3. SOLVE. 4. INTERPRET Check: (in the words of the problem) State:

Explanation / Answer

Understand

We are given the,

X-midterms grads

y- final grads

and we are given the correlation between the x and y, r= 0.70

translate

the scatter plot is the approximate measure of the correlation, and from scatter plot we can’t say axact about the prediction values.

Solve

we are given the value of r=0.70, for the model selection we can calculate the R-square,

R-square= r*r=0.49

So there is only 49% variation is explained by the independent variable about the dependent variable

From the 49% prediction is risky to predict the grade

thnaks

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