Finding Variance and Standard Deviation

One reason why variance and standard deviation from grouped data might differ slightly from the exact value using all raw data is:

• Class midpoints are only approximations of the actual data values within each class.

• Grouped data always adds 1 to the standard deviation.

• Frequency tables have no effect on variance calculations.

• Grouped data calculations always equal the ungrouped results exactly.

Which of the following best describes the standard deviation of a dataset?

• It is the difference between the highest and lowest scores.

• It is the average of all the data values.

• It measures how spread out the data values are around the mean.

• It measures the frequency of each data point.

Variance of a dataset is defined as:

• The cube of the mean.

• The standard deviation multiplied by the mean.

• The average of the squared deviations from the mean.

• The difference between the median and the mode.

You have recorded the height of every student in your school. To calculate variance:

• Use the sample variance formula, dividing by n−1

• Use the population variance formula, dividing by n

• It doesn’t matter which formula you use.

• Use neither; height data cannot have a variance

What is the variance for the data given:
5, 10, 7, 12, 0, 20, 15, 22, 8, 2

• 47.47

• 102.01

• 52.77

• 81

Once you've calculated the mean, and listed the values in a table, what is the next step to calculating the variance?

• Square each value in the data set

• Subtract each value in the data set from the mean

• Subtract the mean from each value in the data set

• Add the mean to each value in the data set

Last step... What is the variance?

• 24.25

• 29.1

• 2

• 4.9

Procedure for finding the ___: find the mean, subtract the mean from every observation in the dataset, square each of those differences, add them all up and then divide by the count of observations minus 1. But do not take the square root.

What does this symbol represent?

• Variance

• Standard Deviation

• Mean Absolute Deviation

• Sigma

What is the variance for the data given:

5, 10, 7, 12, 0, 20, 15, 22, 8, 2