Task 3 Flashcards

1
Q

Define statistical inference

A

draws conclusions about a population or process from sample data

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2
Q

Name 2 types of statistical inference

A
  1. confidence intervals

2. tests of significance

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3
Q

What do the statistical inferences report?

A

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

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4
Q

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

A

random

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5
Q

How do you calculate a confidence interval?

A

C = estimate +or- margin of error

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6
Q

How do you calculate the margin of error?

A

z* x σ/square root of n

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7
Q

Define confidence interval

A

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

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8
Q

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

A

1-C/2

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9
Q

Name 2 desirable characteristics of a confidence interval

A
  1. high confidence 2. small margin of error
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10
Q

Name 3 ways of reducing the margin of error

A
  1. use a lower confidence level
  2. choose a larger n
  3. reduce standard deviation
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11
Q

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

A

(z x σ)/m²

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12
Q

Define significance test

A

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

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13
Q

Differentiate between null and alternative hypothesis

A

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

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14
Q

Define statistical significance

A

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

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15
Q

Define critical value

A

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

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16
Q

Define power

A

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

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17
Q

To increase the power (x3)

A
  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
18
Q

Define a type 1 error

A

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

19
Q

Deine type 2 error

A

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

20
Q

What is alpha the probability of?

A

a type 1 error

21
Q

How do you calculate a type 2 error using power?

A

1-p(type 2 error)

22
Q

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

23
Q

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

A

you halve the p-value

24
Q

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

A

the critical area

25
How do you calculate the ideal sample size?
n = (z*σ/m)² m = margin of error
26
Name one way of reducing the probability of a type 1 error (rejecting a true Ho)
reduce significance level a, however, this is bad for the power as it is then more difficult to reject the Ho
27
How do you calculate z*?
same as z, just signifies alpha level while not being the p-value of it
28
What mathematically symbol cannot a Ho not have?
greater than or less to, must have =
29
Give the z* values for 95%
1.96
30
When searching for the z* for a confidence level remember ____
you divide the confidence level e.g. 95% -> 5%. Divide by 2 as there are 2 sides, now look for z value
31
The confidence level pertains to a) the sample distribution b) the sampling distribution
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?
32
How likely are all values in a confidence level?
equal
33
Power is not applicable ....
in the theoretical situation of a true Ho
34
A z test can only be performed if the distribution of the population is ____
normal
35
The p-value assumes that the ____ is true
Ho
36
What is the critical sample mean?
the sample mean that would lead you to reject the null hypothesis
37
What does SPSS paired samples correlation tell us?
how well 1 group predicts the scores of another
38
Why does power increase when df increases?
increasing df means increasing sample size therefore our t* decreases
39
With df do we round up or down?
be conservative round down!
40
Why are p-values for t-tests in inequalities and z-tests aren't?
This is because its a manual calculation, we cannot find exact df in a table however SPSS can