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PSYC210 > Topic 6 > Flashcards

Topic 6 Flashcards

1
Q

What are characteristics of a population known as?

A

Known as parameters

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2
Q

What are the population parameters?

A
  • Population mean = μ

- Population Standard Deviation = σ

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3
Q

What are characteristics of a sample known as?

A

Known as statistics

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4
Q

What are the sample statistics

A
  • Sample mean = x̄

- Sample standard deviation = s

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5
Q

How do we formulate sampling distributions?

A
  1. Make a guess about population frequency distribution, hypothesise what μ is
  2. Take a random sample from the population
  3. Decide if sample came from a population like the one you guessed in Step 1. (Usually based on how close x̄ is to hypothesised μ)
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6
Q

How do we plot a sampling distribution?

A
  1. Assume normal population distribution with μ and σ
  2. Take repeated samples of size n
  3. Plot x̄ of each sample
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7
Q

In a generic sampling distribution what is the distribution?

A

Normal distribution

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8
Q

In a generic sampling distribution how does the mean relate to population mean?

A

The mean of the sampling distribution is equivalent to the population mean

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9
Q

Describe the standard deviation of a sampling distribution

A

It is depicted as the standard error σx̅. It’s the standard deviation of the sampling distributions

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10
Q

What is the standard error an expression of?

A

A numerical expression of the degree to which means differ from one sample to another

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11
Q

If the standard error is large what will the variability be?

A

Large

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12
Q

If the standard error is small what will the variability be?

A

Small

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13
Q

What does a small standard error tell us about x̄?

A

That x̄ likely close to μ

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14
Q

We wouldn’t normally know the value of σ, how would we estimate it?

A

Using sx̄ = s / square root of n

  • > s = standard deviation of a single sample
  • > n = number of observations in sample
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15
Q

As n increases, what decreases?

A

sx̄ decreases due to decreased sample variability, meaning x̄ is a more accurate estimate of μ

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16
Q

What is the Z Score when looking at sample data?

A

Z = x̄ - μ / σx̅

sample mean - population mean / standard error

17
Q

What is the amount of area beyond Z?

A

The probability of finding a score that distant from the mean on the basis of chance alone

18
Q

Describe the Null Hypothesis

A

Hypothesis that the treatment has no effect and the observed sample mean is drawn from the population

19
Q

Describe the Alternative Hypothesis

A

Hypothesis that the treatment has an effect and observed mean is drawn from population

20
Q

Why would we retain the Null Hypothesis?

A

If observed sample mean could have reasonably been obtained from the distribution suggested by Null

21
Q

Why would we retain the Alternative Hypothesis?

A

If the likelihood is very small that results could have been obtained from the distribution suggested by the Null

22
Q

Describe the Significance level

A

Probability value that defines boundary between rejecting or retaining the Null hypothesis

23
Q

What is the significance level usually set as?

A

0.05, sometimes 0.01

24
Q

What is the region of rejection?

A

Proportion of area in sampling distribution that represents the sample means that improbable if the null is true

25
Q

If Z (zobs) is > or equal to 1.64 what do we do?

A

Reject the null hypothesis

26
Q

What is the critical value?

A

1.64

27
Q

If a Z-Score sits in the region of rejection what does this allow us to do?

A

Reject the null hypothesis

28
Q

Describe a one tailed test and when it’s appropriate to use one

A
  • Test used because we have a directional alternative (can predict the direction of the effect)
  • Used when there is evidence/theory to suggest that treatment will have an effect in a particular direction
29
Q

Describe a two tailed test

A

-Test used when we have a nondirectional alternative

30
Q

Describe the alpha value in a two tailed test

A

It is still 0.05 but now divided by 2 (to account for both sides) = 0.025

31
Q

In which test is it more difficult to reject the null hypothesis?

A

Two tailed test

32
Q

What is Zobs for a 2 tailed test?

A

1.96

33
Q

Which tail test is more powerful?

A

One tail

34
Q

When can the null hypothesis be rejected in a two tailed test?

A

Zobs < or equal to -1.96

Zobs > or equal to 1.96

PSYC210 (28 decks)

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