Week 4

Question 1

one-tailed hypothesis

Answer 1

a directional hypothesis
specific direction of effect
e.g. greater than .50

Question 2

two-tailed hypothesis

Answer 2

a non-directional hypothesis
open ended, no set direction
e.g. not equal to .50

Question 3

alternate hypothesis can be..

Answer 3

directional or non-directional

Question 4

two-tailed

Answer 4

consider both tails of the probability distribution

Question 5

one-tailed

Answer 5

look at only one tail of the probability distribution

Question 5

What should we consider when using a one-tailed test?

Answer 5

easier to find the effect in the expected direction but at the cost of not being able to find the effect in the unexpected direction

Question 6

if we have strong theoretical grounds

Answer 6

and we can expected a particular effect, then you can consider running a one-tailed test
findings replicated over and over by independent researchers may allow us to make directional predictions

Question 7

when do we need to use a two-tailed test?

Answer 7

if there isn’t much evidence to suggest data goes in a expected direction
if testing an intervention that is exploratory
if test a intervention that may cause harm

Question 8

before seeing the data

Answer 8

a decision to use a one or two tailed test must be made and decisions should not be changed

Question 9

pre-registration

Answer 9

researcher declares their intentions ahead of time, other researchers can then verify

Question 10

poor scientific bias

Answer 10

• evidence not supporting claims
• misleading media portrayal
• need for open access
• publication bias (hidden trial)

Question 11

publication bias

Answer 11

a bias towards publishing significant findings so that evidence that finds an effect is reported
studies that don’t find an effect will go unreported, leading to skewed effect

Question 12

issues

Answer 12

fraud

Question 13

ways forward

Answer 13

• open access data, everyone has access to all data to be able to test and validate
• confidence by researchers to submit null findings for publications

Question 14

research hypothesis

Answer 14

a abstract statement of our beliefs about a population parameter

Question 15

statistical hypotheses

Answer 15

the null hypothesis is a formal statement that the effect we are looking for does not exist in the population
the alternative hypothesis is a formal statements that the effect we are looking for does exist in the population

Question 16

null hypothesis

Answer 16

the default assumption
assumed to be true until we can falsify it

Question 17

sampling error

Answer 17

even if we draw two samples from identical populations, they will look different

Question 18

p value

Answer 18

the statement of probability
how likely would it be to observe results at least as extreme as ours if the null hypothesis were true

Question 19

alpha level

Answer 19

a criterion
usually .05

Question 20

if p is less than .05

Answer 20

we reject the null hypothesis

Question 21

if p is grater than .05

Answer 21

we accept the null hypothesis

Question 22

type 1 error

Answer 22

false postive

Question 23

type 2 error

Answer 23

false negative

Question 24

what does the alpha level control?

Answer 24

the type 1 error rate

Question 25

one-tailed hypothesis

Answer 25

specifies an expected direction for the effect

Question 26

two-tailed hypothesis

Answer 26

does not specify a direction of effect

Question 27

once committed to a one tailed…

Answer 27

you cannot detect a statistically significant effect in the unexpected direction