Flashcards in Chapter 12: Sampling Distribution of the Mean and Z-test Deck (34):

1

##
Characteristics of Random Sampling (2)

-population chance of selection?

- members of the population chance of selection?

###
-Each possible sample of a given size has equal chance of being selected

- All members of the population have equal chance of being selected into the the sample.

2

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Why is Random sampling important?(2)

- why is it required?

- what does it assure about the sample?

###
- required to apply laws of probability to a sample

- assures sample is representative of the population.

3

## What is an experiment?

### - tests influence of an IV on a DV

4

## What are hypothesis?

### - statement of prediction

5

## What two kinds of hypothesis are there?

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- Alternative hypothesis (Ha)

-Null Hypothesis (Ho)

6

## What exactly is the Alternative Hypothesis?

### - States there is a difference between the conditions due to the IV.

7

## What exactly is the Null Hypothesis?

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- the logical counterpart of Ha…mutually exclusive and exhaustive.

aka there is no difference between the conditions due to the IV.

8

## What does it mean to be a Directional Hypothesis?

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- specifies a direction of the effect from the IV.

ex: a new drug INCREASES an effect on mood.

9

## What does it mean to be a Nondirectional hypothesis?

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- specifies the IV has an effect, but no direction is stated..

ex: a new drug HAS an effect on mood.

10

## If Ha is nondirectional than what does Ho state?

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- IV has no effect

-ex: New drug HAS NO effect.

11

## If Ha is directional that what does Ho state?

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- IV has no effect or an effect in the opposite direction.

Ex:

Ha= new drug increases mood.

Ho= new drug has NO EFFECT on mood or makes it WORSE..

12

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Results are always evaluated against what?

### the null hypothesis

13

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From the null hypothesis evaluation it is possible to calculate what?

- Now mathematics are available for the probability of what ?

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- calculate probability of chance events

- no mathematics for the probability of Ha

14

## What is the Alpha level used for? (3)

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- calculate the probability of the obtained results if chance alone were operating

- if probability is < critical probability level, reject that Ho

- If reject the Ho, results are statistically significant.

15

## What are the rules for interpreting alpha level?

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- Obtained probability < alpha, reject Ho

Obtained probability > alpha, fail to reject Ho or retain Ho..

16

## Sometimes , chance can be a troll….. hmm…what are the errors possible?

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- Type 1 Error ; reject Ho when it is true...

- Type 2 Error: retain Ho when it is false….

17

##
Fill in the state of reality Table:

Decision |Ho is true | Ho is false

Retain Ho | (A) | (B)

Reject Ho | (C) | (D)

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A) correct decision

B) Type 2 error

C) Type 1 error

D) correct decision

18

## There is a relationship between alpha and what?

### - Type 1 and 2 errors….

19

##
Alpha level usually set at a minimum of it =??

This limits the probability of making what error?

###
- 0.05

- type 1 error

20

## Why not make the alpha more extreme like alpha= 0.01 ????

### - the probability of making a type two error increases.

21

##
Sampling Distribution of a statistic:

- what values are included in this?

-What is the assumption made ?

###
- all the values that the statistic can take

- probability of getting each value under the assumption that it resulted from chance alone

22

## What are the two steps to sampling distribution of a statistic?

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- Calculate the appropriate statistic

- evaluating the statistic based on its sampling distribution

23

## What is the Null-hypothesis population???

### - Set of population scores that would result if the experiment were done on the entire population and the IV had no effect.

24

## What is the sampling distribution of the mean?

### - All the values the mean can take, along with the probability of getting each value if sampling is random from the null hypothesis population.

25

## Explain the empirical approach: Population with μ and σ??

###
- Draw samples of a fixed size N ( whole population)

- calculate mean

- calculate probability of getting each mean if chance alone were operating

26

## Characteristics of Sampling distribution of mean?

###
- distribution of sample means

- has a mean and standard deviation

- μx(bar)= mean of the sampling distribution of means

- σx(bar)= standard deviation of the sampling distribution of mean.

27

##
μx(bar) is equal to what?

what is the calculation for σx(bar) ?

###
-the μ of the original population

- σx(bar)= σ/ \/N (square root of N) also called the standard error of mean

28

## The sampling distribution of the mean is ___ distributed. Depends on ___ of ____ population. Depends on the ___ size (__), which is usually set at around X>_...

###
- normally distributed

- shape, raw score population

- sample size (N)

- >30

29

## When faced with a problem that you need to calculate a Z score, you will be given what?

###
- mu of the population, standard deviation of the entire population

- Xobt of the sample and N of sample

30

## What is Zcrit sued for?

###
- Z crit is the critical region of rejection of Ho

- this is determined by the Alpha level.

31

## What is the rule for Rejecting Ho based on Z crit?

### - If | zobt | > | zcrit |, reject Ho, if not we retain Ho

32

## What is the formula for Zobt???

### Zobt= Xobt- Ux/ σx

33

## What is a critical region?

### - all values of the statistic that allow rejection of Ho which is determined by alpha 0.05 and 0.01!

34