Z-scores

Z score formula

score - mean of scores / standard deviation

Z scores that are the same distance from…

0 have the same chance of occurring

Probability of several shaded areas =

 sum of probability of the shaded areas

Probability of nonshaded areas =

 1 - probability of shaded areas

Given the Z score for a particular score X

 the z-scores table gives the proportion of the population of scores that are larger than score X

Setting probable limits (confidence intervals)

Identify the limits in which we have a specified level of confidence that a randomly selected score in the distribution will fall within a specified range

Dealing with outliers

•  check original data

• remove from dataset

• change the score

Dealing with outliers: change the score:

Replace with next highest score plus one, replace with mean plus/minus 2 X SD (only if it remains the highest/the lowest score)