Calculate the sample mean and sample variance for the following frequency distribution of heights in centimeters for a sample of 8-year-old boys. If necessary, round to one more decimal place than the largest number of decimal places given in the data.
Heights in Centimeters
Class Frequency
121.6-125.2 31125.3-128.9 46129.0-132.6 40132.7-136.3 46136.4-140.0 19

And the variance can be calculated with this formula:

And replacing we got:

Step-by-step explanation:

For this case we can calculate the mean with the following table:

Class                Midpoint (xi)    fi         xi *fi        xi^2 *fi

121.6- 125.2          123.4           31       3825.4      472054.36

125.3-128.9          127.1            46      5846.6      743102.86

129.0-132.6          130.8           40      5232         684345.6

132.7-136.3          134.5           46      6187          832151.5

136.4-140.0          138.2           19      2625.8      362885.56

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Total                                       182      23716.8      3094539.88

And we can calculate the mean with the following formula

And the variance can be calculated with this formula:

And replacing we got:

step-by-step explanation:

rectangles are made up of 4 right angles, which means that a side and a base meet perpendicular to one another.   their slopes then have to reflect perpendicular slopes.   perpendicular slopes are opposite reciprocals of one another.   for example, if the slope of one line is +2/3, then the perpendicular slope to that would be -3/2.   so we look for that combination in our choices.

all of them satisfy that condition (so what's the question, i guess? )