Browse Sampling

22 questions at your level

DifficultyAllLevel 1Level 2Level 3Level 4Level 5

Populations & samples

11 questions

LessonNot started
A conservation group wants to estimate the number of newts in a pond.

They catch 4040 newts, mark each one and return them to the pond.

A week later they catch 2525 newts. 88 of these newts are marked.

Work out an estimate for the number of newts in the pond.
●●●●●Level 33 marksStart
A company employs 12001200 people at three sites.
SiteNumber of employees
Leeds420420
Bristol330330
Cardiff450450
A stratified sample of 8080 employees is to be taken.

(a) Work out the number of employees from Leeds that should be in the sample.

(b) The sample is to contain 2222 employees from Bristol.

Work out the number of employees from Cardiff that should be in the sample.
●●●●●Level 34 marksStart
A town council wants to estimate how many of the town's 24 00024\,000 residents use the town library.

They take a random sample of 300300 residents. 5454 of these residents use the library.

(a) Use the sample to estimate the number of residents in the town who use the library.

(b) The council repeats the survey using a new random sample of 12001200 residents.

Explain why the estimate from this larger sample is likely to be more reliable.
●●●●●Level 33 marksStart
A scientist wants to estimate the number of fish in a lake.

She catches 4040 fish, tags them and returns them to the lake. Later she catches 5050 fish and finds that 88 of them are tagged.

(a) Estimate the number of fish in the lake. [2]

(b) State one assumption she has made. [1]

(c) Give one reason why asking her friends which fish they had seen would NOT be a good way to sample. [1]
●●●●●Level 34 marksStart

Bias & sampling methods

11 questions

LessonNot started
A gym is writing a questionnaire for its members. This is one question from it.

How many hours do you exercise?
  • 0 – 2
  • 2 – 4
  • 4 – 6
(a) Write down two things that are wrong with this question.

(b) Write an improved version of the question. You must include suitable response boxes.
●●●●●Level 34 marksStart
A factory employs 480 workers. They are shown on a staff list, numbered 1 to 480. A manager wants a sample of 60 workers. She chooses worker number 8, then worker number 16, then worker number 24, and so on, taking every 8th worker on the list.

(a) Write down the name of this type of sampling.

(b) Explain why the manager's sample is not a random sample.

(c) Give one advantage of this method over choosing 60 workers at random from the whole list.
●●●●●Level 33 marksStart
A school has 1000 students. Three teachers each choose a sample of 50 students.
  • Mr Ahmed numbers every student on the school register from 1 to 1000 and uses a random number generator to pick 50 numbers.
  • Mrs Bell splits the students into their five year groups and picks students at random from each year group, so that each year group is represented in proportion to its size.
  • Mr Clarke asks the first 50 students to arrive at school one morning.
(a) Write down the name of the sampling method each teacher has used.

(b) Explain why Mr Clarke's sample is likely to be biased.
●●●●●Level 34 marksStart