Experiments and statistics

Question 1

What are the steps in experimental design?

Answer 1

1. formulate hypothesis
2. manipulate variables by translating hypotheses into treatment conditions
3. administer treatment to groups or same p’s
4. measure performance on a response measure

Question 2

Independent variable

Answer 2

treatment conditions

Question 3

dependent variable

Answer 3

Response measures

Question 4

3 types of independent variable

Answer 4

1. Quantitative variables ( represent variation in amounT, E.G. AMOUNT OF DRUG)
2. Qualitative variables ( represent variation in kind or type, E.G. TEACHING STRATEGY)
3. classification ( variables represent characteristics that are intrinsic to thr subjects/participants, E.G. SEX, SPECIES, AGE)

Question 5

Nuisance variables

Answer 5

• potential independent variables which if left uncontrolled could cause systematic influence in the differnet treatment conditions
• if uncontrolled known as confounding variables

Question 6

dependent variable

Answer 6

• what you measure
• a good dependent variable should capture the hypothesised differences

Question 7

what’s one solution for systematic differences in experiments

Answer 7

random allocation - equal chance of participants being in either group

Question 8

completely randomised design (between subjects design)

Answer 8

• each subject randomly assigned to one of the treatment conditions
• helps to prevent confounds

Question 9

repeated measures / within subjects design

Answer 9

• subjects matched closely on some relevant characteristics
• common procedure to treat subjects as a “block” and participants in all treatment conditions of a IV

Question 10

research hypothesis

Answer 10

fairly general statement about the presumed nature of the world that inspires specific experiment
“physical exercise decreases dementia symptoms”

Question 11

statistical hypothesis

Answer 11

• precise statement about the parameters of distributions for different treatment populations
• null and alternative hypotheses
  “mean dementia scores will be lower for the exercise group than for the No-Exercise group (more so than what we would expect to observe by chance)”

Question 12

The null hypothesis

Answer 12

• tests seek to accept or reject it
• 𝑯_𝟎: 𝝁_𝟏=𝝁_𝟐= 𝝁_𝟑
• this is the same as saying that no treatment effects are present in the population

Question 13

The alternative hypothesis

Answer 13

• if the treatment parameters do not satisfy the null hypothesis ( one or more of the differences between treatment means is greater than expected by chance) REJECT the null hypothesis
• parameters are not equal between treatment conditions

Question 14

what is the typical alpha value?

Answer 14

0.05

Question 15

when do you reject H0?

Answer 15

• if the p value is less than alpha its statistically significant and we reject H0
• otherwise fail to reject H0

Question 16

Type 1 error

Answer 16

false positive

Question 17

type 2 error

Answer 17

false negative