W2: Practical

Question 1

What does this show?

Answer 1

drug 1 was scoring better than the placebo group and drug 2 was scoring additional benefit of this new drug

Question 2

For interaction effect a

Answer 2

clustered bar chart is better

Question 3

What is an interaction effect?

Answer 3

An interaction effect occurs when the effect of one variable depends on the value of another variable.

Question 4

• Line graphs can be quite useful when you got

Answer 4

time series data (measurements over many time points)

Question 5

Example of interaction effect - (3)

Answer 5

• So for drug 1, this seemed to be as effective as drug 2 for early onset Alzheimer
• Drug 1 not very effective for late onset Alzhiemer and not much difference between drug 1 and placebo for that group
• Whereas, drug 2 seems to be more effective for both types of early and late onset Alzheimer’s

Question 6

What are z-scores?

Answer 6

A measure of variability: The number of standard deviations from the population mean or a particular data point is

Question 7

Z scores are a standardised measure and ignore

Answer 7

measurement units

Question 8

Why should I care about Z scores? - (2)

Answer 8

Z-scores allow researchers to calculate the probability of a score occurring within a standard normal distribution

Enables us to compare two scores that are from different samples (which may have different means and standard deviations)

Question 9

How to read positive z score table to get percentile? - (2)

Answer 9

first colum contains first part of z score (whole number and decimal point)

top row contains remaining deicmal point

Question 10

How to read positive z score table to get percentile? example- (2)

Answer 10

if z score is 1.25 then.. look left column for 1.2 and top row for 0.05

Question 11

If trish takes a test and gets a score of 25 and shows her z score is 1.25 and percentle is 0.8944 it shows that

Answer 11

89.4% of students performed worse than Trish

Question 12

Who performed better Trish or Josh?
89.4% students performed worse than Trish
84.1% students performed worse than Josh

Answer 12

Trish

Question 13

68% of scores are within

Answer 13

1 SD of mean

Question 14

95% of scores are within

Answer 14

2 SDs of mean

Question 15

99.7% of scores are within

Answer 15

3 SDs of the mean

Question 16

narrow CIs indicate higher

Answer 16

power

Question 17

wider CIs indicate

Answer 17

low statistical power (bad).

Question 18

If CIs overlap shows

Answer 18

two means not significantly different

Question 19

If CIs do not overlap it shows

Answer 19

two means are significantly different

Question 20

Null hypothesis is typically a hypothesis of

Answer 20

no difference (0)

Question 21

We assume the null hypothesis is

Answer 21

true

Question 22

We collect evidence to REJECT the

Answer 22

null hypothesis

Question 23

We can never say that the null hypothesis is

Answer 23

FALSE

Question 24

TheP valueor calculated probability is the estimated probability of us

Answer 24

finding an effect when the null hypothesis (H0) is true.

Question 25

p value equals to

Answer 25

probability of observing a test statistic at least as a big as the one we have if the null hypothesis were true.

Question 26

Statistical significance does not equal

Answer 26

importance

Question 27

The reason why statistical significance does not equal importance due to 2 reasons - (2)

Answer 27

1. p = 0.049, p = 0.050 are essentially same and former is statistically sig 2. Importance is dependent upon exp design/aims

Question 28

Statistical Sig does not equal importance as importance dependent upon experimental design/aims - example

Answer 28

A statistically significant weight increase of 0.1Kg between two adults experimental groups may be less important than the same increase between two groups of babies.