BIOL132 - L6

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  • Created by: Katherine
  • Created on: 07-06-16 21:47
What is a z test?
We use a z test is our sample is very large, such as greater than a couple hundred subjects.
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When do we use a z test if our sample is small?
If our estimate of the standard error of the population mean is a known parameter.
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When do we use a t test?
When our sample is small and the standard error of population mean must be estimated from our sample statistics
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Do we use z test if we know the standard deviation and the sample is about 30?
Yes
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Do we use a z test if we don't know the standard deviation and the sample size is below 30?
No - we use a t-score
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What do descriptive statistics do>
They provide basic measurs of a distribution of scores.
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What do interential statistics allow?
Allow inferences to a larger population from the sample
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How does inference work>
Representatvie sample from two groups are selected. Variables are tested. Means from each group are compared. Researchers conclude that measured differences between either result from chance or, reflect true difference.
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What is a conclusion drawn regarding...
The role group membership plays in observed differences
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What does statistical testing do>
It looks are the probabiltiy that this result occurred by chance - that if we ran this experiment 100 times we'd find that really there is no diffeerence between treatment or none.
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What is the p-value of 50/100?
p=0.5 (50%)
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What is the p value of 10/100?
p=0.1 (10%)
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When does convention occur? When there is an accepted probabilty of at least...
p
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Who decided on the 0.05 rule?
Ronald Fisher
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What are related samples?
Those where the same experimental subjects provide two sets of scores e.g. without any training in maths and then later after training.
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What are independent samples?
Where independent groups of experimental subjects, e.g. comparing males and females, subjects in group A or B.
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What sort of sampe was the rat experiment>
Independent
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When should parametric tests be used>
When the level of measurement is continous/interval or ratio (more than ordinal), the distribution of the scores are normal, calculations assume normal distribution, the variances of both variables are roughly equal or homogeneous.
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What is a histogram?
It is a graph
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What does parametric mean>
It means the the test uses statistics based on the normal distribution.
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When comparing treated vs untreated rats, can we use parametric>
Yes - independent samples, the level of measurement os continuous/interval/ration/ and the data will be relatively normally distributed
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What are the types of tests used to test differences between 2 samples?
Independent samples t test, mann whitney test, related samples test, wilcoxon test.
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If I have independent samples which are parametric, what test should i used?
Independent samples t test
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If I have independent samples non parametric data, what test should i use?
Mann whitney test
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If I have related samples parametric data, which test should i use?
Related t samples t test
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If I have related samples non parametric data test, which test should i use?
Wilcoxon test
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What is independent sample?
If the values in one sample reveal no information about those of the other sample, then the samples are independent.
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What is a related sample?
If the values in one sample affect the values in the other sample, then the samples are dependent.
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What is the effect of the t value on the p value?
The larger he value of t, the lower the p value, the more likely we reject H0.
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What is it called when we don't know whether the treatment may harm, help or have no effect, when we test for difference between means>
two tailed t test
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How many ways are there to state out alternative hyptohessi>
2
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What is the first way?
h0: control mean = treatment mean and H1: control mean not equal to treatment mean
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What is the second wat>
h0: control mean = treatment mean 1: control mean < treament mean h1: control mean > treatment mean
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What do we expect in a non directional hypothesis?
Extreme results that are some distance greater than or less than the controll mean. But were not sure which.
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What do we expect in the second hyptohesis>
A directional hypothesis, one trailed test - we expect our result to be greater than the control mean, or we expect out result to be less than the control mean. we only test on of these two outcomes.
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What is the critical value?
0.05 level.
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The one taield p value is ... the 2 tailed p value?
Half
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Card 2

Front

When do we use a z test if our sample is small?

Back

If our estimate of the standard error of the population mean is a known parameter.

Card 3

Front

When do we use a t test?

Back

Preview of the front of card 3

Card 4

Front

Do we use z test if we know the standard deviation and the sample is about 30?

Back

Preview of the front of card 4

Card 5

Front

Do we use a z test if we don't know the standard deviation and the sample size is below 30?

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