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15 Cards in this Set
- Front
- Back
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what does a z-score indicate? |
the distance, measured in standard deviation units, that a score is above or below the mean |
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why are z-scores important? |
z-scores can be used to interpret scores from any normal distribution of interval or ratio scores |
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2 factors z-score size depends on |
1) the size of the deviation 2) the size of the standard deviation |
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what is a z-distribution? |
it is the distribution that results after transforming a distribution of raw scores into z-scores |
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what are the steps for using the standard normal curve to find a raw score's relative frequency or percentile? |
(1) convert the raw score to z
(2) use z with the z-tables to find the proportion of the area under the appropriate part of the normal curve
(3) this proportion is the rel. f OR use it to determine percentile |
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what are the steps for finding the raw score that cuts off a specified relative frequency or percentile? |
1)in column B or C of the z-tables, find the specified rel. f (or rel. f converted from the percentile)
2) identify the corresponding z
3) transform z into its raw score --> this score is the cut off score |
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what are the steps for finding a sample mean's relative frequency? |
1) compute the standard error of the mean
2) transform the sample mean into a z-score
3) use z-tables to find area proportion under the normal curve
4) this proportion = rel. f (or can be used to determine percentile) |
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z-distribution characteristics |
1) z-distribution has the same shape as the raw score distribution
2) the mean of any z-distribution is 0
3) the standard deviation of any z-distribution is 1 |
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z-table assumption |
assumes a normal distribution |
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z-tables used for 2 things |
1) given a z-value, can look at where that value falls on the probability distribution
2) given some criteria (probability) what z-values corresponds to that probability |
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z-table column a |
absolute value of z-scores |
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z-table column b |
area between the mean and z-score |
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z-table column c |
area in the tail (proportion of scores that are higher than your positive z-scores/lower than your negative z-scores) |
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(column B) + (column C) = |
.50 ALWAYS |
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column C x 100 = |
percentile |
