Summarising Data Flashcards
Descriptive statistics
Techniques that help describe a set of data
Inferential statisitcs
Methods that use the limited
information from samples to answer general questions about populations
Statistic
A summary value that describes a sample. A common example of a statistic is the average score for a sample.
Parameters
A summary value that describes a population. A common example of a parameter is the average score for a population.
Frequency distribution
A tabulation of the number of individuals in each category on the scale of measurement. A frequency distribution displays two sets of information:
- The set of categories that make up the scale of measurement.
- The number of individuals with scores in each of the categories
Descriptive statistics
Methods that help researchers organize, summarize, and simplify the results obtained from research studies
Inferential statistics
Methods that use the results obtained from samples to help make generalizations about populations
Histogram
A histogram shows a bar above each score so that the height of the bar indicates the frequency of occurrence for that particular score. The bars for adjacent scores touch each other
Polygon
A polygon shows a point above each score so that the height of the point indicates the frequency. Straight lines connect the points, and additional straight lines are drawn down to the horizontal axis at each end to complete the figure
Bar graph
A bar graph is like a histogram except that a space is left between adjacent bars
Central tendency
Central tendency is a statistical measure that identifies a single score that defines the center of a distribution. The goal of central tendency is to identify the value that is most typical or most representative of the entire group
Mean
The mean is the most commonly used measure of central tendency. The mean is computed by adding the scores and dividing the sum by the number of individuals
Median
The median is the score that divides a distribution in half, so that 50% of
the individuals have scores that are less than or equal to the median. Usually, the median is used for data sets in which the mean does not provide a good representative value
Mode
The mode is the score or category with the greatest frequency. In a frequency distribution graph, the mode identifies the location of the peak (highest point) in the distribution
Variance
The calculation of standard deviation begins by computing the average squared distance from the mean. This average squared value is called variance
Standard deviation
Square root of the variance and provides a measure of variability by describing the average distance from the mean
Degrees of freedom
n - 1, where n is the number of scores in the sample.
the average squared distance for a sample is computed by dividing the sum of the squared distances by n - 1
Normal curve
A symmetrical, bell-shaped frequency polygon representing a normal distribution.
Normal distribution
A theoretical frequency distribution that has certain special characteristics
Kurtosis
How flat or peaked a normal distribution is
Mesokurtic
Normal curves that have peaks of medium height and distributions that are moderate in breadth
Leptokurtic
Normal curves that are tall and thin, with only a few scores in the middle of the distribution having a high frequency
Platykurtic
Normal curves that are short and more dispersed (broader), when there are many scores around the middle score that all have a similar frequency
Positively skewed distribution
A distribution in which the peak is to the left of the centre point, and the tail extends toward the right, or in the positive direction
Negatively skewed distribution
A distribution in which the peak is to the right of the centre point, and the tail extends toward the left, or in the negative direction
Z-score / standard score
A measure of how many standard deviation units an individual raw score falls from the mean of the distribution
Standard normal distribution
A normal distribution with a mean of 0 and a standard deviation of 1
Probability
The expected relative frequency of a particular outcome
Percentile rank
A score that indicates the percentage of people who scored at or below a given raw score
