Acertain test preparation course is designed to students improve their scores on the lsat exam. a mock exam is given at the beginning and end of the course to determine the effectiveness of the course. the following measurements are the net change in 6 students' scores on the exam after completing the course: 23,18,23,12,13,23using these data, construct a 80% confidence interval for the average net change in a student's score after completing the course. assume the population is approximately normal.

Interval [16.34 , 21.43]

Step-by-step explanation:

First step. Calculate the mean

Second step. Calculate the standard deviation

As the number of data is less than 30, we must use the t-table to find the interval of confidence.

We have 6 observations, our level of confidence DF is then 6-1=5 and we want our area A to be 80% (0.08).  

We must then choose t = 1.476 (see attachment)

Now, we use the formula that gives us the end points of the required interval

where n is the number of observations.

The extremes of the interval are then, rounded to the nearest hundreth, 16.34 and 21.43

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