Ch 6.3 - Standard Deviation and Z-score

Activity: Do Action! activity on page 278/279 #1-5

variance: the average squared difference of the scores from the mean

HW: page 275 #1, 3, 5, 9

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6.3February-24-153:00 PM

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Problems with variance:more 'weight' is given to extreme (very large or small) values•gives units squared, which is different than the units of the data•

standard deviation: the square root of the variance; the average distance of the scores from the mean

Ex1 - Std Dev. in Graphs

Which graph has a greater standard deviation?

graph 1 graph 2

If the variation on graph 1 is 1.5, what is the std. dev.?

What would graph 1 look like if the standard deviation were 1.8?

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What would graph 1 look like if the standard deviation were 1.8?

Ex 2 - Std Dev. from data

Find the mean and std. dev.1 2 3 4 2 1 2 4 2 3 3 3 4 1 1 2 3

What would to the std dev if the values were all 1 higher?

z-score: the number of std dev an observation is from the mean

Ex 3: z-score

A data set has a mean of 5 and a std dev of 1.2, determine the z-scores for data with values of 6.2 and 3.

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HW: pg 286 #1, 2, 3, 4, 6, 7a

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