Percent / percentage point
If a rate rises from 20% to 30%, it increases by 10 percentage points. The relative increase is (30−20)/20 × 100 = 50%.
True or false?
Read the concept ↗Research in 60 Seconds.
One idea, one example, one memorable insight.
Correlation
Ice cream sales and swimming both increase in summer. A shared factor, such as temperature, can explain their association.
True or false?
Read the concept ↗A strong correlation alone proves cause and effect.
Mean and median
For 3, 4, 4, 5 and 34, the mean is 10 and the median is 4. The large extreme value pulls the mean upwards.
True or false?
Read the concept ↗Extreme values can affect the arithmetic mean.
Variable
“Time to campus” and “transport mode” are two variables in a student survey. Belonging to the same person does not make them one variable.
True or false?
Read the concept ↗Coding categories as 1 and 2 makes them quantitative variables.
Double-barrelled question
“Are you satisfied with the library’s quietness and opening hours?” mixes an experience someone likes with one they may dislike.
True or false?
Read the concept ↗Combining two issues into one satisfaction question always improves measurement.
Outlier
Most sessions last 10–40 minutes, but one lasts 900. You investigate whether it remained open or was recorded incorrectly.
True or false?
Read the concept ↗An outlier must be a data-entry error.
Random assignment
You assign 80 volunteers to two study techniques by lottery. Assignment is random, but volunteers may not represent all students.
True or false?
Read the concept ↗Random assignment and random sampling address different problems.
Missing data
Fifteen of 100 students leave travel expenditure blank. Replacing blanks with zero assumes they had no expenditure.
True or false?
Read the concept ↗A blank income field always means zero income.
Recall bias
You ask about all travel delays last year. A recent very bad journey may influence how someone recalls the entire period.
True or false?
Read the concept ↗