analysis and distributions

Question 1

what is a scatterplot?

Answer 1

display relations between two quantative variables

Question 2

how to know if a relationship is strong or weak

Answer 2

1. strong = points lie close to the line
2. weak = points are widely scattered

Question 3

what does it mean when variables are correlated?

Answer 3

variables are related

Question 4

what is the purpose of a correlation analysis? (3)

Answer 4

determine

1. if linear relationship
2. direction of relationship
3. strength of relationship

Question 5

what are correlation coefficients

Answer 5

number between 1 and -1

tells us strength and direction of relationship

Question 6

what does a positive correlation coefficent mean?

Answer 6

positive relationship

positive correlation

Question 7

what does a negative corellation coeeficient mean?

Answer 7

negative relationship

negative correlation

Question 8

what is the difference between linear and non linear relationship?

Answer 8

linear = measuring correlations okay

non linear = cant measure correlations

Question 9

what are the two types of coefficient

Answer 9

1. pearson r
2. spearman r

Question 10

what is pearson r coefficient?

Answer 10

1. calculated from raw scores
2. suitable for interval or ratio data
3. highly affected by outliers
4. not suitable for skewed data

Question 11

what is spearman r coefficient?

Answer 11

1. calculated from ranking raw scores
2. suitable for ordinal data
3. marginally affected by outliers
4. suitable for skewed data

Question 12

what is a density curve?

Answer 12

histogram distribution of scores of ppt

useful when lots of ppt

Question 13

what do density curves show?

Answer 13

the overall pattern of a distribution

Question 14

density curve + median

Answer 14

point that divides area into two equal parts

Question 15

density curve + quartiles

Answer 15

point that divide area under curve into quarters

Question 16

density curve + mode

Answer 16

positions at the peak of the curve

Question 17

density curve + mean

Answer 17

balancing point of the curve

Question 18

what does symmetrical density curve mean?

Answer 18

mean = median = mode

Question 19

what does skewed density curve mean?

Answer 19

mean does NOT = median and mode

Question 20

how is a normal distribution described?

Answer 20

by a normal curve

Question 21

what is a normal curve? (5)

Answer 21

1. symmetrical
2. single peaked
3. tail meet x axis at infinity
4. location determined = mean
5. shape determined = standard devation

Question 22

how to assume if data is normally distributed?

Answer 22

statistical tests

Question 23

what to do if data is not normally distributed

Answer 23

use a non parametric test

Question 24

what are z scores / standard scores?

Answer 24

allow us to compare values from different data sets

Question 25

what is the standard score z of an observation ?

Answer 25

deviation of x from mean / standard deviation

Question 26

how to get a standard normal distribution

Answer 26

standardising all values of a normal distribution

Question 27

what does a standard normal distribution do?

Answer 27

allow us to determine proportions of observations

Question 28

why are parametric & non parametric tests used?

Answer 28

test significant differences between data sets

Question 29

what are 2 key things about parametric tests?

Answer 29

1. make assumptions about population parameters 2. require interval or ratio data

Question 30

what does a violation of test assumptions leads to?

Answer 30

erroneous interpretations of the data

Question 31

3 key things about non parametric tests

Answer 31

1. make no assumptions on popular parameters 2. can use nominal data 3. not as powerful as parametric tests

Question 32

why is the chi square test for goodness of fit used? (4)

Answer 32

1. used on unrelated data 2. used to answer q about proportions 3. used to compare different levels of a variable 4. compare sample proportions to population proportions

Question 33

what are observed frequencies?

Answer 33

number of ppt measured in indivdual catergories

Question 34

what are expected frequencies

Answer 34

frequencies predicted by the null hypothesis