Faculty Head: Mrs Little

LOB: To explore how statistics may come up on your exam paper.

Starter:

Title: Numerical and statistical skills

Planners

Date: 08/05/2018

Some words you need to know:

Ratio: A comparison between two things. In geography this is most often seen where?

As the scale on a map.

1:50,000 What does this mean?

For every 1 cm on the map there are 50,000 in the real world

Magnitude – the size of something. What do we use the term for in geography?

Frequency – how often something happens. What could you asked about the frequency of in geography?

Measures of central tendency:

These are your averages:

Mean – Add up all the values in a set of data then divide by the number of values.

Median – the middle value of a set of data – write them out in order. What do you do if there is an even number of values?

Find the mean of the two middle values.

Measures of central tendency:

Mode – the value that occurs most frequently in a set of data.

What is the modal class?

Where data is grouped into categories, this is the category with the largest number of values.

Measures of spread of data:

Measures of central tendency (averages) are great for showing average values in a data set. However, they give no indication how the data is spread out around that middle value.

Any ideas of any measures we can use to show this?

Range. What is this?

Difference between highest and lowest value.

Dispersion graphs are a way we can show how the data is spread out visually.

To learn about these, lets look at a sample Q from your sample exam papers set 1.

Complete Q4.6 and have a go at 4.7.

Measures of spread 2: Interquartile range.

The median is the middle value of a data set. This splits the data in half.

Each half can then be split again into half (effectively dividing the data into quarters.

The value that splits each half of the data is called a quartile.

You can either just use the graph to find this or use the following formulas:

UQ = (n+1)/4 LQ = (3n+1)/4 (These formulas give the position of the UQ and LQ, not the actual value.)

Show the median, upper quartile and lower quartile on your dispersion graph.

The more likely graph to come up in your exam:Scattergraph.

Scattergraphs show bivariate data – what is this?

Data for two variables that can be considered to be related.

Scattergraphs are used to show the relationship of two variable.

The independent variable goes on the X axis and the dependent variable (the one that changes as a result of the independent variable) goes on the y axis.

Which is the independent variable out of GDP and energy consumption.

Scattergraphs

Once the points have been plotted on a scattergraph, you should draw a line of best fit showing the overall trend of the data. How to draw a line of best fit:

• It doesn’t have to go through 0!

• There should be equal numbers of points either side of the line.

• The direction of a line of best fit indicates:

What is a positive correlation?

As one variable increases, so does the other.

What is a negative correlation?

As one variable increases, the other decreases.

How to interpolate and extrapolate trends:

Interpolation involves estimating an unknown value from within a data set.

Extrapolation involves estimating an unknown value from outside the dataset.

For the scattergraph you have been given,

1. Draw a line of best fit.

2. Describe the relationship shown.

3. Suggest what the river depth when the river is 5m across.

4. Is this extrapolation or interpolation?

5. Suggest what the river depth will be when the river is 9m wide.

6. Is this extrapolation or interpolation?

Percentiles:

Used to indicate the value below which a given % of observations will fall.

The 80th percentile is the value in a data set below which 80% of values will fall.

What other name can be given to the…

50th percentile?

25th percentile?

75th percentile?

Percentage increase and decrease:

How do you work out % change?

To calculate the % increase/decrease between 2 numbers…1. Work out the difference between the two numbers.

(subtract the old value from the new value.)2. Divide the increase by the original (old) value.3. Multiply the answer by 100 to give you a %.

Population StructureLearning Objectives:

1. To know what a population pyramid is and what it shows.

2. To be able to draw a population pyramid.

3. To know how to interpret population pyramids.

A population pyramid is...

The horizontal axis shows...

The vertical axis shows...

Population pyramids.

These are used to show the structure of a countries population.

This means the proportions of men and women at different ages in the country. This is useful to see whether there are lots of young, people of working age or older people in a country.

Population pyramids show a lot about a country if you know how to interpret them. See tips on understanding population pyramids sheet.

Annotate the population pyramids to say what they show.