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Statistics > Variables > Flashcards

Variables Flashcards

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

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

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

A

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

25
Q

What variables are used in logistic regression

A

A continuous predictor variable

A binary outcome variable

26
Q

What does autocorrelation show

A

The degree of correlation of the same variables between two successive time intervals

27
Q

Nominal variable

A

Variable used amounts and numbers eg how tall, how old

28
Q

Ordinal variables

A

Variables that can be ordered eg finishing place in a race

29
Q

Alternate hypothesis

A

The original hypothesis that assumes influence of one variable on another

30
Q

When do you use a one sample t test

A

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
Q

When do you use a two sample or independent t test

A

When studying groups from two separate samples

Eg from two towns

32
Q

When do you use a paired t test

A

If the means come from the same population

Eg before and after an experiment takes place

33
Q

What is a t-test used for

A

To compare the means of two groups

34
Q

What is normal distribution

A

Data that is symmetrically distributed with no skew

Also known as a bell curve

35
Q

When is an ANOVA and MANOVA test used

A

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
Q

What does a chi squared test show

A

How well sample data fits what is expected

37
Q

Three types of categorical variables

A

Binary
Nominal
Ordinal

38
Q

Discrete variable

A

A nominal variable that is finite

39
Q

Null hypothesis

A

The hypothesis that assumes no relationship exists between two or more variables

40
Q

What is the p value

A

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
Q

What do comparison statistics tests do

A

Look for differences among group means

42
Q

When is a pearsans r correlation test used

A

With linear relationships
Two quantitative variables
Any distribution

43
Q

What does a standard error show

A

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
Q

What variables are used in multiple linear regression

A

2 or more continuous predictor variables

1 outcome variable

45
Q

What does mahalanobis distance show

A

The distance between two points in data

Useful for finding outliers

46
Q

What are three types of comparison tests

A

T test
ANOVA
MANOVA

47
Q

Independent variable

A

Variables that are changes to see the effect on another variable

48
Q

What is the durbin-Watson test

A

a test statistic to detect autocorrelation in the residuals from a regression analysis.

49
Q

What does winsorizing data mean

A

Replacing an outlier or outliers with the next highest/lowest value that is not an outlier

50
Q

What is a univariate and multivariate outlier

A

Univariate - an outlier for just one variable

Multivariate - an outlier for numerous variables

51
Q

When is a t test used

A

To determine if a process or treatment (change in one variable) actually effects the population of interest or if there is no relationship

52
Q

When can a t test be used

A

When comparing the means of two groups only

53
Q

Confounding variable

A

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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