Standard Deviation!. Let’s say we randomly select 9 men and 9 women and ask their GPAs and get these data: MENWOMEN 0.901.50 2.003.00 1.43.00 2.002.50.

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Presentation transcript:

Standard Deviation!

Let’s say we randomly select 9 men and 9 women and ask their GPAs and get these data: MENWOMEN Men 2.44 Women 2.78 Can we conclude that the average GPA of ALL women at South is higher than the average of ALL men?

Standard Deviation The standard deviation is a measure of the degree each data point in the set of data points varies (or deviates) from the mean The wider the spread of scores, the larger the standard deviation.

Standard Deviation For data that has a normal distribution, 68% of the data lies within one standard deviation of the mean One SD

How to calculate the standard deviation: 1.Calculate the mean (M) of a set of data

How to calculate the standard deviation: 2. Subtract the mean from each point of data to determine (X-M) MENWOMEN 0.90 – 2.44= – – – – – – – –

How to calculate standard deviation: 3. Square each of the resulting numbers to determine (X – M) 2

How to calculate standard deviation : 4. Add the values from the previous step together to get ∑(X-M)

How to calculate standard deviation: 5. Calculate (n-1) by subtracting 1 from your sample size. Your sample size is the total number of data points you collected. N - 1 for men = 9 – 1 = 8 N – 1 for women = 9 – 1 = 8

How to calculate standard deviation: 6.Divide the answer from ∑(X-M) 2 by the answer from (n-1) to find ∑(X-M) n - 1

How to calculate standard deviation: 7. Calculate the square root of your previous answer to determine the standard deviation Men √1.09 = 1.04 Women √0.51 = 0.71

This means that… In men, 68% of all students sampled have a GPA that falls within 1.04 grade points of the mean. – MEAN PLUS 1.04 = 3.49 – MEAN MINUS 1.04 = 1.40 In women, 68% of all students sampled have a GPA that falls within 0.71 grade points of the mean. – MEAN PLUS 0.71 = 3.49 – MEAN MINUS 0.71 = 2.07

Graph results to find out: So, are women smarter?