Unit 1 - Descriptive Statistics Flashcards
What are the measures of central tendency?
Mean, Median, Mode.
How is the mean calculated?
Add all numbers together, divide by number of participants.
How is the median calculated?
Middle number, put numbers into order ranging from lowest to highest, choose middle.
How is the mode calculated?
Most occurring.
What is a strength of the mean?
Accurate average, and takes into account all the scores.
What is a weakness of the mean?
Outlier scores can skew the mean to not reflect most participants.
What is a strength of the median?
Not affected by outlier scores, so results will not be skewed.
What is a weakness of the median?
Does not take into account all scores.
What is a strength of the mode?
Can be used for non-numerical data.
What is a weakness of the mode?
Impossible to calculate if all data is different, or the may be more than one mode.
What are the measures of dispersion?
Range, Variance, Standard Deviation.
How is the range calculated?
Largest score minus smallest score.
How is the variance calculated?
For each condition, calculate the mean. Within each, subtract each participant’s score from the mean for that condition (‘d’ difference). Then square each ‘d’ score (d^2). Then add all d2 scores together to get Ed2, then subtract by n-1.
How is standard deviation calculated?
Square root of variance.
What is a strength of range?
Quick and easy to calculate.
What is a weakness of range?
Data can be skewed by outliers, only takes into account top and bottom values.
What is a strength of variance?
Takes into account all values, less likely to be affected by outliers.
What is a weakness of variance?
Only takes into account the squared values, not original units the data was first in.
What is a strength of SD?
Takes into account all data, expressed in same unit as original.
What is a weakness of SD?
Time consuming and more difficult to calculate than range.
How to convert fractions to a percentage?
Divide top of fraction by bottom, multiply by 100.
How to convert a percentage to a fraction?
Write percentage over 100, simply fraction, if not a whole number, multiply top and bottom by 10 for every number after the decimal point.
How to find actual number of a percentage of an amount?
Divide amount by 100 and multiply by percentage.
How to find actual number represented by fraction of an amount?
Divide amount by the denominator (bottom) and multiply by numerator (top)
What is a frequency table?
A way of presenting data - tally chart. WHEN = observation
HOW = tally of behaviour
What is a line graph and when and how is it used?
Shows behaviour changes over time. Includes X and Y axis, labelled.
What, when and how do you use a pie chart?
Works well with nominal data, enables researcher to present percentages, includes labels and titles. WHEN = observation
HOW = percentage converted into decimal (divide by 100), 360 multiplied by decimal to calculate the degree.
What, when and how do you use a bar chart?
Conveys information about frequencies through height of the bar.
WHEN = experiments
HOW = (1 mark) data plotted accurately, (1 mark) detailed title, (1 mark) both axis labelled (y axis - mean rating) (x axis - what you’re measuring), (1 mark) mentioning mean rating, y axis must start at 0, bars must be spread apart.
What, when and how do you use a histogram?
Conveys information about frequencies through area of the bar, used with continuous data, emphasised by the category width. 0< x < 2 (time), frequency (number of people), time (class width), frequency / class width (frequency density). WHEN = experiments HOW = title, axis labelled, bars touching, area represents frequency, unusual class width.
When and how are scatter graphs used?
WHEN = correlations HOW = pattern and strength. ‘uphill’ = positive correlation, ‘downhill’ = negative correlation, ‘spread apart’ = no correlation.
How are ratios calculated?
= divide the amount of by total number of parts and then multiply by the original ratio.
