Statistics Revision- Short Answers

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What is a biological population?
A collection of individuals of the same species at a particular location at the same time
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What is a statistical population?
Individuals within a specified time or space out which inferences are to be made
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Define variable
Characteristics of a population which differ from individual to individual
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What is systematic sampling?
Systematic sampling uses information about the population to select a more "representative" sample.
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What is cluster sampling affected by?
It is affected by clumping and grouped sampling units.
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Does standard error decrease or increase with an increasing sample size?
Decreases
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Does the number of replicates increase or decrease with an increasing within-treatment variation?
Increases
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What is pseudoreplciation?
Pseudoreplication is non-independence between measures, claiming to be independent replicates. They are not true replicates.
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What is a test statistic a measure of?
The test statistic (t) is a measure of the size of the effect, difference or relationship.
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How is the test statistic measured?
Variation between groups/ variation within groups
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What are the three types of data type?
Nominal, Ordinal and Interval Scale.
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What is standard deviation?
Standard deviation is the measure of variation around the mean. The average amount by which the observations in a sample differ from the mean.
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What is standard error?
The average amount by which sample means differ from the population mean.
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What 2 graphs present nominal data?
Pie chart and stacked bar chart
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What graph illustrates a difference in mean values between categories?
Bar Chart
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What graph illustrates a relationship between two variables?
Scatterplot
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What shape is a perfect normal distribution curve?
A bell shape
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Define probability
Probability: The proportion of the total number of repeats in which A would actually occur. The likelihood of the event occurring.
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Which scale does probability only make sense for?
Discrete outcomes
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What two parameters determine the distribution of a normal distribution curve?
The mean and the standard deviation.
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95% of the probability of a normal distribution lies within how many standard deviations of the mean?
1.6
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Variables are (3 blanks)
Continuous, qualitative and discrete
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If distribution is very asymmetric, what measure of location is best?
The Median
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When is the mode most useful for measuring location?
When the data is discrete and few values occur
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What kind of distributions is the inter-quartile range useful for?
Asymmetric distributions
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What other two hypothesis are there, as well as null?
The alternative hypothesis and the experimental hypothesis
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When is data transformed?
Data is transformed if the normality or equal variance assumption breaks down.
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What test is appropriate to compare two non-parametric independent data samples?
A Mann-Whitney Test
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When is the poisson distribution used?
It is used when random events in a certain area or time interval have no fixed upper limit.
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In a poisson distribution, is the mean and variance the same?
Yes, as lambda is equal to both the mean and the variance.
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What test is appropriate for comparing observed and expected frequencies?
A chi-square goodness of fit test.
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How do you calculate expected frequencies?
Row total X Column total/ overall total
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how do you calculate the degrees of freedom of a chi-square distribution?
v= (number of rows - 1) x (number of columns - 1)
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What does the Kruskal Wallis test for differences?
The medians
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Other cards in this set

Card 2

Front

What is a statistical population?

Back

Individuals within a specified time or space out which inferences are to be made

Card 3

Front

Define variable

Back

Preview of the front of card 3

Card 4

Front

What is systematic sampling?

Back

Preview of the front of card 4

Card 5

Front

What is cluster sampling affected by?

Back

Preview of the front of card 5
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