Descriptive Statistics
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Define central tedency
the tendency for the values of a random variable to cluster round its mean, mode, or median.
Define mean, median and mode
mean - average median - middle value of data set mode - most common number
what are the 4 measures of variability
• Standard deviation • Interquartile range • Confidence intervals • Z - scores
Define standard deviation
The dispersion of values around the mean
Define interquartile range
which is the difference between the first and third quartiles.
Define confidence intervals
a range of values so defined that there is a specified probability that the value of a parameter lies within it.
Define Z - scores
A z-score describes the position of a raw score in terms of its distance from the mean when measured in standard deviation units
What is a high and low standard deviation
Low standard deviation means data are clustered around the mean, and high standard deviation indicates data are more spread out.
Define correlation
Correlation is a statistical measure that expresses the extent to which two variables are linearly related
Define regression
a measure of the relation between the mean value of one variable (e.g. output) and corresponding values of other variables
Defije multiple regression
explains the relationship between multiple independent or predictor variables and one dependent or criterion variable
Define p value
• P-value is the probability that a random chance generated the data or something else that is equal or rarer • P value is a number between 0 and 1
What is the P value threshold for statistical significance
• Threshold for statistical significance is most commonly <0.05
Lower the P value = what
Greater amount of statistical significance
What does a P value of 0.05 denote
5% probability that the results happened by chance
Define linear regression
Linear regression expresses the relationship of two variables by fitting a linear equation to observed data
Explain what a linear regression graph will look like for each value R = 0 R = -1.0 R = +1.0 R = +0.06
R = 0 will result in a circle on data plot R = -1.0 will result in a diagonal line from top left to bottom right with dots along line R = +1.0 will result in a diagonal line from bottom left to top right with dots along line R = +0.6 will result in diagonal line from bottom left to top right but dots are spread a bit away from line (Same for -0.6 but different direction)
Define pearsons correlation
• Pearson’s correlation coefficient is the test statistics that measures the statistical relationship, or association, between two continuous variables.
Define high, medium and low degree of correlation for r
• High degree: If the coefficient value lies between ± 0.50 and ± 1, then it is said to be a strong correlation. • Moderate degree: If the value lies between ± 0.30 and ± 0.49, then it is said to be a medium correlation. • Low degree: When the value lies below + . 29, then it is said to be a small correlation.
What does correlation not tell u
does not tell you whether one variable causes the other
Define and explain regression equation
• Y = bX + C • Y is the dependent variable • X is the independent variable • B is the slope or regression coefficient • C is the intercept of the Y axis
Define forced entry regression
Produce one R value
Define stepwise regression
Produce one or more R values for variables that explain variance
Define hierarchical regression
Produces R values at each step