hypothesis testing and statistical significance

Question 1

confidence intervals

Answer 1

how confident can we be that the results in our sample represent the population

it is an interval estimate of where the population mean might lie in the population.- e.g. we are 95% certain that the population mean lies between 8 and 10

in psychology we use 95% confidence interval based on SD OF 2(1.96).

Question 2

standard error

Answer 2

standard deviation divided by square root of the sample size.
you need the standard error to calculate your confidence interval.

Question 3

confidence interval calculation

Answer 3

you times the standard error by 1.96 (sd)

then you plus or minus it from the mean- and this is your range that u are 95 certain the population mean lies between.

Question 4

issues with standard error

Answer 4

smaller samples have larger confidence intervals

so larger the sample the better the estimate of the population

Question 5

hypothesis- alternative

Answer 5

H1
There is a difference/relationship between the variables
population mean from the 2 groups are not equal

directional- important you have previous research to back this up

can be causal- specific causal influence- only used if you are doing a controlled experiment

or non causal-suggests particular characteristics of behaviour without reference to causation.

can be directional or non directional- if enough previous evidence we can do directional.
directional= one tailed test
non directional= two tailed tests

Question 6

hypothesis- null

Answer 6

H0
when we do statistical testing we translate it to the null hypothesis
there is no difference/relationship
population groups are equal

Question 7

hypothesis and falsifiability

Answer 7

we need to be able to test hypotheses generated by a theory that prove the theory incorrect

Question 8

p value

Answer 8

5%= 0.05
you ask spss of the probability of finding such a difference if there was no relationship in the population (if the null was true)

if P value is less than 0.05 we can reject the null hypothesis

Question 9

Inferential stats

Answer 9

tell us about the population- draws conclusions about the population based on what we observed in our sample e.g. is the results we saw in the sample likely going to happen in the population- we make inferences by checking the p value

lots of statistical tests are used

need specific assumptions before you do a certain test

Question 10

T tests (parametric)

Answer 10

William Gosset (1908)- 
referred to as 'student t test'
difference between two groups/means- can be on 2 separate groups/ one group on 2 occasions/ whether one group compares to a specific mean (we don't cover this one).

Question 11

parametric vs non parametric

Answer 11

PARAMETRIC- based on population parameter (e.g. mean or SD)- they assume your data plots in a normal distribution- so you need to screen your data beforehand- more power= ability to find a effect/difference/relationship when using smaller sample sizes
Main overview of assumptions= .ratio or interval of DV
.population should be normally distributed
.variation of populations should be equal(only valid when doing tests comparing 2 means)
.no outliers/extreme scores

NON-PARAMETRIC- distribution free- don’t make any assumptions about the distribution- these are less sensitive meaning you need larger sample sizes (less what we call power)

Question 12

T TEST assumption checking

Answer 12

.must be interval or ratio
.’reasonably’ normally distributed
.if comparing 2 different groups the variances across populations must be equal. (Levens test checks this)
.no outliers/extreme scores

Question 13

degrees of freedom in a T test

Answer 13

one sample t test= N-1
related t test= N-1
unrelated t test= (N-1)+(N-1)

Question 14

one tailed or 2 tailed ?

Answer 14

2 tailed preferred- non directional/null
spss will automatically run 2 tailed

to do 1 tailed in spss u divide p value by 2

Question 15

Types of T tests

Answer 15

1. within participants/repeated measures/paired sample t test- advantage of this is it has higher power as natural differences are controlled for
   2.