Numerical & Statistical Skills Flashcards
All 18 cards in this deck
How many square metres are there in 1 square kilometre?
1 000 000 m² (1000 m × 1000 m).
What is the formula for working out what percentage a part is of a total?
percentage = (part ÷ total) × 100
What is the difference between the magnitude and the frequency of an event?
Magnitude is its size or strength; frequency is how often it happens.
Give one reason why the total score from an environmental quality survey may be an unreliable basis for a conclusion.
All categories are given equal weighting, although some matter more than others for quality.
What are the steps to find the median of a set of data?
e.g. 12, 7, 9, 15, 4- Put the values in order: 4, 7, 9, 12, 15
- Pick the middle value: 9
- If there are two middle values, find their mean.
What are the steps to find the interquartile range?
e.g. 2, 4, 6, 8, 10, 12, 14, 16- Order the data and split it into a lower half and an upper half: 2, 4, 6, 8 | 10, 12, 14, 16
- LQ = median of the lower half: 5; UQ = median of the upper half: 13
- IQR = UQ − LQ = 13 − 5 = 8
What is the range of a set of data?
The highest value minus the lowest value — a measure of spread.
What is the modal class?
The class (group) with the highest frequency, i.e. containing the most values.
What is the formula for percentage change?
percentage change = (change ÷ original value) × 100. Always divide by the starting value.
What does the 90th percentile of a data set tell you?
90% of the values in the data set lie below it.
True or false? Showing only part of a time series can hide a longer-term trend.
True. Selecting a short period can make a rise or fall look typical when the full record shows otherwise.
What is a positive correlation on a scatter graph?
As one variable increases, so does the other; the points run from lower left to upper right.
True or false? Points running from the top left to the bottom right of a scatter graph show a negative correlation.
True. As one variable increases, the other decreases.
Where should a line of best fit be drawn on a scatter graph?
A straight line through the centre of the scatter, with roughly as many points above as below; it need not touch any point.
What is the difference between interpolating and extrapolating a trend?
Interpolating reads a value within the range of the data; extrapolating extends the trend line beyond the data to predict.
True or false? A mean calculated from a small sample is less likely to be representative of the whole area than one from a large sample.
True. A larger sample captures more of the variation, so its mean is more likely to represent the whole area.
What does the interquartile range of a data set measure?
The spread of the middle 50% of the values: the gap between the upper quartile and the lower quartile.
What does a scatter graph show if there is no correlation?
The points are scattered with no clear pattern, so there is no relationship between the two variables.