19 subjects take part in a math exam, followed by an intervention and a post-test. from their pre-test/post-test difference scores, there was a mean difference of 13.19, with a standard deviation of 22.3. calculate the 95% confidence interval of the difference. round your final answer to two decimal places.

the answer is 489

step-by-step explanation:

the simplified form is

step-by-step explanation:

we want to simplify the expression,

let us change the middle bar to a normal division sign to obtain,

we multiply the first fraction by the reciprocal of the second fraction to obtain,

we factor to obtain,

we cancel the common factors to get,

we simplify to get,

the correct answer is b