week 9, validity + descriptive statistics

Question 1

how can we combine some of the elements of different non-experimental designs to make them stronger?

Answer 1

non-equivalents control group design with pre and post test

Question 2

what is a quasi-experimental designs

Answer 2

interrupted time-series design
measuring a variable over time both before and after
-no control group !!

Question 3

what are some threats to internal validity for interrupted time series design designs?

check slide 13 for slide 1

Answer 3

selection bias -> less concern bc participants comapred to themselves

potential testing effects are distributed along the entire time series

regression to the mean, one data point may be extreme but rest are unlikely to be affected

Question 4

what is cross sectional design

Answer 4

compare language, memory, emotional response, social skills, etc

Question 5

how to combat generation cohort effect when you test different ages?

Answer 5

longitudinal design, test same kids throughout their lives

Question 6

what is time-lag design

Answer 6

different cohorts are tested in different years, but age is kept constant ( 12 yr olds from 3 different years)

if theres no dfference then generation nor year of test matters

Question 6

what is a confounding variable for longitudinal design

Answer 6

year of test, could have history and testing effects

Question 7

what is a cohort-sequential design, what is a risk of it?

Answer 7

combines cross sectional, longitudinal, time-lag and requires replication and extension.

selective attrition is still an issue

Question 8

internal validity in experimental research

Answer 8

to what extent are changes in the DV caused unambiguously by changes in the IV
- have all alternative explanations been adequately ruled out?

Question 9

what factors reduce internal validity?

Answer 9

1. violations of random assignment (no control group, non equivalent groups)
   2.presence of confounds

Question 10

external validity in non-experimental research

Answer 10

are the results derived from a sample generalizable to whole population?
- concerned with sampling methods

Question 11

external validity in experimental research

Answer 11

generalizability of experimental results to other people or situations (dif contexts/outside of lab)

Question 12

what factors reduce external validity?

Answer 12

1. violations of random sampling (cant generalize to pop)
   -replicate findings in other samples of same pop, other pop etc
2. small sample sizes, over/underestimate effect
3. artificiality of experimental setting (talking about political views w strangers)

Question 13

laboratory observations have… internal validity and …. external validity

naturalistic obersvations have internal validity and …. external validity

Answer 13

1. high, low
2. low,high

Question 14

unsure if DV changed due to my manipulation of the IV or not (due to low internal validity)

but !! im pretty sure it would generalize (due to high external validity)

Question 15

how do we increase generalizablity of results? what is this called

Answer 15

combine internally valid experiments with externally valid field studies, method triangualtion

Question 16

generalizability of results is not always the goal, externally invalid but internally valid studies can answer important theoretical questions that can affect human behaviour inside and outside the lab

Answer 16

on to slide 2

Question 17

what is descriptive statistics and inferential statistics?

Answer 17

1. describes and summarizes data
2. draws inferences from data

Question 18

what does a histogram plot?

Answer 18

frequency of occurrence

Question 19

what is the central tendency?

Answer 19

a measure of what value the individual scores tend to center on.
tells us about the whole sample

Question 20

what are types of central tendency?

Answer 20

1. mode -> most common value (used for categorical variables, nominal scales), not useful with continuous scales
2. median -> middle value, useful for ordinal scales, interval, and ratio but NOT nominal

3.mean -> arithmetic average,

Question 21

mean median and mode can have the same values but normally don’t

Question 22

what does it mean for a distribution to be right skewed?

Answer 22

• some values are extremely high

Question 23

what does it mean for a distribution to be left skewed?

Answer 23

• some values are extremely low

Question 24

use the stroop test to define congruous condition

Answer 24

Color word matches the ink color, easy with fast response

Question 25

use the stroop test to define incongruous condition

Answer 25

color word doesn’t match the ink color, harder with slower response

Question 26

means are affected by the distribution, therefore it is sometimes better to use the median

Question 27

what is variability in the data?

Answer 27

1. how clustered are the data?
   2.how different are the scores?

Question 28

what are measures of variability?

Answer 28

1. range -> between highest and lowest value

2.variance -> average squared deviation from the mean, average squared distances -> variance.
we only care about magnitude of variance

3.standard deviation -> average deviation from the mean
we only care about magnitude of variance
square roots variance to restore metric to og unit

Question 29

what is the relationship between variables in a scatterplot

Answer 29

the 2 variables move together, both up or both down
or
they move opposite direction,
one up one down

Question 30

what does correlation coefficient (r) care about

Answer 30

• relationship between x and y
• size -> strength of relationship
  -sign -> direction of relationship

Question 31

if r=0 then what kind of relationship?

Answer 31

zero relationship

Question 32

-1 ≤ r ≤ +1

Answer 32

-1 = negative perfect
+1 = positive perfect

Question 33

what does it mean for 2 variables to be related?

Answer 33

tells you there is a relationship between variables (but not why)

Question 34

one possibility is a casual relationship, give an example

Answer 34

paying nurses more causes an increase in household incomes

Question 35

finding a correlation does not imply that one variable causes the other, what does this mean?

Answer 35

correlation does not equal causation

Question 36

what are difficulties interpreting correlations?

Answer 36

1. third-variable problem: another variable caused the change

2.Directionality problem: dont know if variable x caused variable y or other way

3. Selection bias:systematic differences between the comparison groups

Question 37

what are spurious correlations?

Answer 37

third variable problem & selection bias often lead to correlations that do not indicate a casual relationship.

Question 38

what is appropriate language to describe a correlation?

Answer 38

• association
  -relationship
  -correspondence
  -correlation

Question 39

what is inappropriate language to describe a correlation?

Answer 39

-determine
-cause
-lead
-shape
-influence

Question 40

we conduct experiments to say something about causation