# Head Start to A-Level Maths: Statistics and Probability

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What is the population?
The population is the whole group you want to investigate.
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Wha is a census?
If you collect information from every single member of the population
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What is a sample?
A selection from the population to represent the whole group.
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How can you obtain reliable results from a sampling frame?
The sampling fame should include as much of the population as possible.
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How can you limit bias as much as possible?
• Choose from the correct population and don’t exclude anyone. • Choose your sample at random. • Make sure your sample is big enough.
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What is the Simple Random Sampling method?
It gives every member of the population an equal chance of being in the sample, so it's unbiased.
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How to select a Simple Random Sample?
Start by giving every member of the population a unique number. Then generate a list of random numbers and match them to the population members.
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What is a variable?
A quantity that can take different values.
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What are qualitative variables?
They take non-numerical values – e.g. colours of cars.
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What are quantitative variables?
They take numerical values – e.g. temperature.
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What are the different types of quantitative data?
Discrete and Continuous
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What are discrete variables?
They take certain values within a particular range – e.g. shoe size.
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What are continuous variables?
They take any value within a particular range – e.g. length.
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What is the formula for class width?
Upper class boundary - Lower class boundary
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What is the formula for a histogram?
Frequency = Frequency Density x Class Width
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How to find the modal class in grouped data?
The modal class is the class with the highest frequency density.
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How to estimate the mean in grouped data?
To estimate the mean, you’ll need to add extra columns – one for the mid-point of each class and another for Frequency x Mid-point.
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What are outcomes?
The different things that can happen in a probability experiment.
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What is an event?
The thing you want to find the probability of.
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What is the formula you can use to work out the probability of an event when all the possible outcomes are equally likely?
P(event) = Number of outcomes where event happens / Total number of possible outcomes.
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How do you calculate the expected frequency of a result?
Expected frequency of a result = Probability x Number of Trials
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What is the universal set?
Is the group of things that the elements of the sets are selected from. It’s everything inside the rectangle.
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What is the union?
The union of sets A and B, ( A U B), contains all elements in either set A or set B. It’s everything inside the circles.
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What is the intersection?
The intersection of sets A and B, (A n B), contains all the elements in both set A and set B. It’s where the circles overlap.
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What is the complement?
The complement of set A, (A’), contains all members of the universal set that aren’t in set A.
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## Other cards in this set

### Card 2

Wha is a census?

#### Back

If you collect information from every single member of the population

### Card 3

#### Front

What is a sample?

### Card 4

#### Front

How can you obtain reliable results from a sampling frame?

### Card 5

#### Front

How can you limit bias as much as possible?