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Variables Flashcards

(53 cards)

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1
Q

When is a Spearman’s rho correlation test used

A

Non linear variable
Two ordinal, interval or ratio variables
Any distribution

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2
Q

What variable are used in simple linear regression

A

1 continuous predictor variable

1 continuous outcome variable

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3
Q

What does a z score show

A

How many standard deviations a value is from the mean

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4
Q

What is the empirical rule

A

In standard deviation 68% of scores are within 2 standard deviations of the mean
95% are within 4
99.7% are within 6

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5
Q

What do correlation tests do

A

Check if variables are related without hypothesising a cause and effect relationship

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6
Q

Composite variable

A

A combination of other variables

Is used when data is being analysed not generated

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7
Q

What is a correlation coefficient

A

A number between 1 and -1 that shows the strength and direction of a relationship between variables

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8
Q

What is homogeneity of variance

A

The assumption that the variance within each group being compared is similar across each group

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9
Q

Control variable

A

Variable that is kept constant throughout the experiment

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10
Q

Latent variable

A

A variable that is not measured directly but inferred via proxy

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11
Q

What is standard deviation

A

How much a single data point differs from the mean of the sample
Shows how much variability is in the dataset

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12
Q

Why is a standard error important

A

It helps estimate how well your sample data represents the whole population

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13
Q

How is the standard deviation calculated

A

It is the square root of: the sum of each value minus the population mean squared then divided by the number of values in the population

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14
Q

Continuous variable

A

A nominal variable that can be infinite

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15
Q

Binary variables

A

Categorical variable with only two possible answers

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16
Q

When is a chi squared test used

A

With categorical independent and dependent variables

In place of Pearson’s if it does not meet the assumptions

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17
Q

categorical variable

A

Represent a group of data such divided into categories eg gender, hair colours

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18
Q

What are the three types of t tests

A

One sample
Two sample/independent
Paired

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19
Q

Dependent variable

A

Variable that is impacted on by the independent variable but not changed directly by the researcher

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20
Q

When is a point-biserial correlation test used

A

Linear variables
One binary variable and one quantitative variable
Normal distribution

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21
Q

What is a linear variable relationships

A

When the results of one variable depend on another

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22
Q

What three assumptions are made with parametric tests

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A

Homogeneity of variance
Normality of data (bell curve) - only applies to quantitative data
Independence of observations - the variables included are not related

23
Q

What are regression tests used for

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A

Looking for cause and effect relationships

Used to estimate the effect of one or more continuous variable on another

24
Q

What are residuals

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A

The difference between the observed value and the mean value that a particular model predicts for that observation.

25
What variables are used in logistic regression
A continuous predictor variable | A binary outcome variable
26
What does autocorrelation show
The degree of correlation of the same variables between two successive time intervals
27
Nominal variable
Variable used amounts and numbers eg how tall, how old
28
Ordinal variables
Variables that can be ordered eg finishing place in a race
29
Alternate hypothesis
The original hypothesis that assumes influence of one variable on another
30
When do you use a one sample t test
When comparing a group against a known standard value Eg national population average Comparing the acidity of a liquid to a ph neutral of 7
31
When do you use a two sample or independent t test
When studying groups from two separate samples | Eg from two towns
32
When do you use a paired t test
If the means come from the same population | Eg before and after an experiment takes place
33
What is a t-test used for
To compare the means of two groups
34
What is normal distribution
Data that is symmetrically distributed with no skew | Also known as a bell curve
35
When is an ANOVA and MANOVA test used
ANOVA - when there is one dependent variable from different samples - eg exam results from multiple schools MANOVA - when there are two or more dependent variable eg math results, science results, English results individually
36
What does a chi squared test show
How well sample data fits what is expected
37
Three types of categorical variables
Binary Nominal Ordinal
38
Discrete variable
A nominal variable that is finite
39
Null hypothesis
The hypothesis that assumes no relationship exists between two or more variables
40
What is the p value
The measure of the probability that an observed result or difference occurred only by random chance A Lower p value shows a greater statistical significance
41
What do comparison statistics tests do
Look for differences among group means
42
When is a pearsans r correlation test used
With linear relationships Two quantitative variables Any distribution
43
What does a standard error show
How different the population mean is likely to be from the sample mean Shows how much the sample mean would varying you were to repeat a study using new samples form the same population
44
What variables are used in multiple linear regression
2 or more continuous predictor variables | 1 outcome variable
45
What does mahalanobis distance show
The distance between two points in data | Useful for finding outliers
46
What are three types of comparison tests
T test ANOVA MANOVA
47
Independent variable
Variables that are changes to see the effect on another variable
48
What is the durbin-Watson test
a test statistic to detect autocorrelation in the residuals from a regression analysis.
49
What does winsorizing data mean
Replacing an outlier or outliers with the next highest/lowest value that is not an outlier
50
What is a univariate and multivariate outlier
Univariate - an outlier for just one variable | Multivariate - an outlier for numerous variables
51
When is a t test used
To determine if a process or treatment (change in one variable) actually effects the population of interest or if there is no relationship
52
When can a t test be used
When comparing the means of two groups only
53
Confounding variable
A variable that masks the true effect of another variable in an experiment Can occur when another variable is closely related to a variable being studied but is not controlled for

Statistics (7 decks)

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