Flashcards · Maths · Statistics
Histograms and Sampling
-
What is the formula for frequency density?
Frequency divided by class width.
-
What does the area of a bar in a histogram represent?
The frequency.
-
How do you find a frequency from a histogram bar?
Frequency density multiplied by class width.
-
What label goes on the vertical axis of a histogram?
Frequency density.
-
Why are there no gaps between the bars of a histogram?
The data is continuous.
-
How do you estimate the frequency in part of a class?
Take that fraction of the class's frequency.
-
What is a population?
Everyone or everything you want to know about.
-
What is a sample?
The part of the population that you actually measure.
-
What is a biased sample?
One where some members of the population are more likely to be chosen than others.
-
What is a random sample?
One where every member has an equal chance of being chosen.
-
What is a stratified sample?
A sample with each group represented in proportion to its size.
-
How do you find the number from a group in a stratified sample?
Group size divided by population size, times the sample size.
-
What is the capture-recapture formula?
\(N = \dfrac{M \times n}{m}\).
-
50 fish are marked, and a sample of 40 has 8 marked. What is the population estimate?
\(\dfrac{50 \times 40}{8} = 250\).
-
What assumption does capture-recapture make?
The marked animals mix evenly and the population does not change.
-
Why does a larger sample usually give a better estimate?
It is more likely to represent the whole population.