Task 3

Question 1

Define statistical inference

Answer 1

draws conclusions about a population or process from sample data

Question 2

Name 2 types of statistical inference

Answer 2

1. confidence intervals

2. tests of significance

Question 3

What do the statistical inferences report?

Answer 3

both report probabilities that state what would happen if we used the inference method many times

Question 4

When you use stat. inference, you assume the data came from what kind of sample or experiment?

Answer 4

random

Question 5

How do you calculate a confidence interval?

Answer 5

C = estimate +or- margin of error

Question 6

How do you calculate the margin of error?

Answer 6

z* x σ/square root of n

Question 7

Define confidence interval

Answer 7

for a parameter is an interval computed from sample data bu a method that has probability C of producing an interval containing the true parameter value

Question 8

How do you find the area on either side of a confidence interval

Answer 8

1-C/2

Question 9

Name 2 desirable characteristics of a confidence interval

Answer 9

1. high confidence 2. small margin of error

Question 10

Name 3 ways of reducing the margin of error

Answer 10

1. use a lower confidence level
2. choose a larger n
3. reduce standard deviation

Question 11

What is the formula for the sample size for desired maring of error?

Answer 11

(z x σ)/m²

Question 12

Define significance test

Answer 12

a formal procedure for comparing observed data with a hypothesis whose truth we want to address
-> results are expressed in terms of a probability

Question 13

Differentiate between null and alternative hypothesis

Answer 13

Ho: the statement we want to prove wrong
Ha: the statement we want to prove right

Question 14

Define statistical significance

Answer 14

the chosen boundary for the p-value, if the p-value becomes equal to or smaller than this number than this number, we reject the Ho, siginificant

aka alpha and usually = 0.05

Question 15

Define critical value

Answer 15

a value z* with a specified area to its right under the standard normal curve, it is the p-value of exactly 5%

Question 16

Define power

Answer 16

opposite of type 2 error, the probability of correctly rejecting the incorrect Ho

Question 17

To increase the power (x3)

Answer 17

1. increase alpha (bad solution as type 1 error increases)
2. increase n (makes estimator more efficient by decreasing standard error)
3. bigger effect (however we cannot control this)
   I μtrue - μ I

Question 18

Define a type 1 error

Answer 18

rejecting Ho when it is true (i.e. accepting Ha)

Question 19

Deine type 2 error

Answer 19

accepting Ho when it is not true (i.e. rejecting Ha)

Question 20

What is alpha the probability of?

Answer 20

a type 1 error

Question 21

How do you calculate a type 2 error using power?

Answer 21

1-p(type 2 error)

Question 22

If your alpha is too high you increase the probability of a type _ error and decrease the probability of a type _ error

Answer 22

1, 2

Question 23

What happens to the p-value on 2 sided tests?

Answer 23

you halve the p-value

Question 24

If zobs is greater than z* the z-score therefore falls into ______

Answer 24

the critical area

Question 25

How do you calculate the ideal sample size?

Answer 25

n = (z*σ/m)²

m = margin of error

Question 26

Name one way of reducing the probability of a type 1 error (rejecting a true Ho)

Answer 26

reduce significance level a, however, this is bad for the power as it is then more difficult to reject the Ho

Question 27

How do you calculate z*?

Answer 27

same as z, just signifies alpha level while not being the p-value of it

Question 28

What mathematically symbol cannot a Ho not have?

Answer 28

greater than or less to, must have =

Question 29

Give the z* values for 95%

Answer 29

1.96

Question 30

When searching for the z* for a confidence level remember ____

Answer 30

you divide the confidence level e.g. 95% -> 5%. Divide by 2 as there are 2 sides, now look for z value

Question 31

The confidence level pertains to

a) the sample distribution
b) the sampling distribution

Answer 31

b I mean look at the formula, it contains the SE and sure isn’t the confidence interval supposed to show the chances of a population mean lying within it?

Question 32

How likely are all values in a confidence level?

Answer 32

equal

Question 33

Power is not applicable ….

Answer 33

in the theoretical situation of a true Ho

Question 34

A z test can only be performed if the distribution of the population is ____

Answer 34

normal

Question 35

The p-value assumes that the ____ is true

Answer 35

Ho

Question 36

What is the critical sample mean?

Answer 36

the sample mean that would lead you to reject the null hypothesis

Question 37

What does SPSS paired samples correlation tell us?

Answer 37

how well 1 group predicts the scores of another

Question 38

Why does power increase when df increases?

Answer 38

increasing df means increasing sample size therefore our t* decreases

Question 39

With df do we round up or down?

Answer 39

be conservative round down!

Question 40

Why are p-values for t-tests in inequalities and z-tests aren’t?

Answer 40

This is because its a manual calculation, we cannot find exact df in a table however SPSS can