Ch6: Normal curve, Standardization, and Z scores

normal curve

bell shaped curve that is unimodal, symmetric, and defined mathematically

sample size

• important in relation to normal curve

• as this increases, distribution more closely resembles a normal curve, spreads out

standardization

convert individual scores from normal distributions to shared normal distribution with a known mean, standard deviation, and percentiles

z score

number of standard deviations a particular score is from a mean

calculating a particular z score:

• subtract mean of population from raw score

• divide by standard deviations of the population

z score to raw scores:

• multiply z score by the population standard deviation

• add population mean to the product

central limit theorem

distribution made up of the means of many sample

distribution of means

composed of many means that are calculated from all possible sample of given size, taken from same population

• standard deviations of the distribution tends to be less than the standard deviation of the population (standard error)

scores vs means

scores:

• symbol for mean: mew

• symbol for spread: standard deviation (curved o)

• name for spread: standard deviation

means:

• symbol for mean: mewM

• symbol for spread: standard deviationM

• standard error