Research methods 19 | Descriptive statistics Flashcards
What are the three measures of central tendency?
Mean, median, and mode
How is the mean calculated?
Sum of all values divided by number of values
What is the main advantage of the mean?
Uses all data points (sensitive measure)
What is the main disadvantage of the mean?
Easily distorted by outliers
How is the median calculated?
Middle value when data is ordered (average of two middle values if even number)
What is the advantage of the median?
Not affected by extreme values/outliers
What is the mode?
Most frequently occurring value in dataset
When is the mode most useful?
For categorical data or when looking for most common value
What are measures of dispersion?
Statistics that describe how spread out data is (e.g., range, standard deviation)
How is range calculated?
Maximum value minus minimum value
What is the limitation of range?
Highly affected by outliers
What does standard deviation measure?
How spread out scores are around the mean
How do you interpret a high vs low standard deviation?
High SD = more spread out; Low SD = clustered near mean
What is the formula for calculating a percentage?
(Part ÷ Whole) × 100
How do you calculate percentage change?
[(New - Old) ÷ Old] × 100
What does a positive correlation indicate?
As one variable increases, the other increases (0 to +1 coefficient)
What does a negative correlation indicate?
As one variable increases, the other decreases (0 to -1 coefficient)
What does a zero correlation mean?
No relationship between variables (coefficient near 0)
In salary data: 10k,15k,15k,15k,20k,24k,24k,26k,36k,195k - what is the mode?
£15,000 (most frequent)
In the same salary data, what is the median?
£22,000 (middle of £20k and £24k)
In the same salary data, what is the mean?
£38,000 (sum ÷ number of values)
If Class A has SD=5 and Class B has SD=12, which has more consistent scores?
Class A (lower SD means less variability)
How would you calculate 24% of 250?
0.24 × 250 = 60
If A-level students increase from 595 to 724, what is the percentage increase?
21.7% [(724-595)/595 × 100]
