Exam Revision Flashcards
nominal
variables that have no numerical value and instead are categories (e.g. catholic, christian etc.).
ordinal
no numerical value as such but something that can somewhat be calculated (e.g, low, medium, high).
equal interval
can be numerical, must have an equal distance (e.g. 5000, 10000, 15000).
frequency tables
arranged to that there are three columns.
- number
- frequency
- percentage
grouped frequency tables
the same as normal frequencies except numbers are grouped into equal intervals in order to reduce the number of rows.
histograms
arranged so that the x variable, the horizonal axis is the number and that the y axis is the frequency.
frequency polygon
developed using a histogram. each maximum value of each number is taken and then plotted into a graph.
unimodal
has one maximum peak.
has one mode.
bimodal
two peaks and therefore two values that have a greater frequency than the others.
multimodal
multiple peaks, occurs when there are multiple values with a greater frequency than the others. i.e. multiple modes.
negative skew
The left tail is longer; the mass of the distribution is concentrated on the right of the figure. The distribution is said to be left-skewed, left-tailed, or skewed to the left, despite the fact that the curve itself appears to be skewed or leaning to the right; left instead refers to the left tail being drawn out and, often, the mean being skewed to the left of a typical center of the data.
positive skew
The right tail is longer; the mass of the distribution is concentrated on the left of the figure. The distribution is said to be right-skewed, right-tailed, or skewed to the right, despite the fact that the curve itself appears to be skewed or leaning to the left; right instead refers to the right tail being drawn out and, often, the mean being skewed to the right of a typical center of the data.
leptokurtic
thinner than the normal distribution. there is a sharper peak around the mean.
platykurtic
distribution is broad and flat.
characteristics of the Z distribution
Mean =0
SD=1
criterion variable
dependent variable
predictor variable
independent variable
positive correlation
A positive correlation is a relationship between two variables where if one variable increases, the other one also increases.
negative correlation
Negative correlation is a relationship between two variables in which one variable increases as the other decreases, and vice versa.
Difference between strong and weak correlation
The more closer the value of r is to its endpoints, the stronger is the correlation. If the value of r is close to 0 then we conclude that the correlation is weak and hence there is no linear relationship between the variables.
descriptive statistics
summarise data
inferential statistics
generalise data from a sample into a population.