LECTURE 4

Question 1

descriptive value for population

Answer 1

parameter

Question 2

descriptive value for sample

Answer 2

statistic

Question 3

common examples of descriptive stats

Answer 3

Question 4

method for simplifying and organizing data: organized pic of entire set of scores, shows relative individual

Answer 4

frequency distribution
also grouped frequency distribution
USUALLY IN HISTOGRAM!

Question 5

positive skew has

Answer 5

scores bunched at low values, tail at high

Question 6

negative skew has

Answer 6

scores bunched at high values, tail at low

Question 7

leptokurtic

Answer 7

high, thin peak

Question 8

platykurtic

Answer 8

low, broad peak

Question 9

kurtosis refers to

Answer 9

peakedness of a distribution

Question 10

besides histogram, how else can you show a frequency distribution?

Answer 10

stem and leaf

Question 11

3 common techniques of central tendency

Answer 11

mode, median, mean

Question 12

advantage of median

Answer 12

relatively unaffected by extreme scores!
-good for ordinal, interval/ratio data

Question 13

mean is most commonly used measure of central tendency and needs scores that are….

Answer 13

interval/ratio!

Question 14

when should you not report the mean?

Answer 14

-skewed data
-modifying data by adding/discarding scores (need to recalculate mean)
-nominal data

Question 15

in a symmetrical distribution, mean, median and mode will all be…

Answer 15

equal!

Question 16

in skewed distribution, mode is near ___, median is ___, mean is ____

Answer 16

mode: peak
median: between
mean: tail

Question 17

variability is…

Answer 17

descriptive statistics: measures degree to which scores are spread out in a distribution
inferential stats: measure of how accurately any 1 score/sample represents entire population

Question 18

variability can be measured with

Answer 18

range
SD/variance

Question 19

range is

Answer 19

total distance covered by distribution (highest score-lowest)

Question 20

SD is

Answer 20

average distance between a score and the mean

Question 21

___% of scores are in +/-1 SD of the mean

Answer 21

70%

Question 22

% of scores within 2 SD of mean

Answer 22

95%

Question 23

% scores within 3 SD of the mean

Answer 23

99%

Question 24

z score of 2 is how many SDs

Answer 24

2

Question 25

z =

Answer 25

score - mean / SD

Question 26

If you know the proportion/probability then you can look up….

Answer 26

z-score! (and vice versa

Question 27

With z score of 1.96, there is a ___% chance of being in the tail

Answer 27

2.5% for 2 tailed test

Question 28

You must know the ___(population or sample) SD to use z-distribution

Answer 28

POPULATION
for most research, we don’t know this. So you rarely see z-stats (usually t or F)

Question 29

What is central limit theorem?

Answer 29

as sample size increases (approaches 30), it becomes a normal distribution (SD gets smaller)
*easier to get in the tail and have significant result with larger sample!
MEAN BTWN SAMPLE AND POP WILL BE CLOSE TO SAME VALUES