Stats: Sample types and data Flashcards
What are the two types of non-random sampling?
Quota and opportunity
Describe quota sampling.
The population is divided into groups that reflect the whole population, or people are selected to fill a quota
Describe opportunity sampling.
Sample of first people available that fit the characteristics
What is the difference between a census and a sample?
- A census measures every member of a population
- A sample measures a subset of the population
Give an example of when a census is a bad idea?
- When the population is very large
- When the testing damages/destroys the population, e.g testing limits of equipment
What are the 3 types of random sampling?
- Simple Random
- Systematic
- Stratified
Describe Simple random sampling.
Every member of the population has a completely equal chance of being tested (e.g assigned numbers and a generator used)
Describe systematic sampling
Each unit of a sample is assigned a number and are selected at regular intervals
Describe Stratified sampling.
Random sample from strata groups
What does ‘cleaning’ data mean?
removing anomalies/outliers
What is the mode of data?
Value that appears most often
What is the mean of data?
Sum of all values/ number of values
What is the median of data?
Middle value when data is placed in order
What is the range of data?
Largest value - smallest value
What is a common definition of an outlier?
k(IQR) + Q3
or
Q1- k(IQR)
What is the difference between continuous and discrete data?
Continuous = data can take any value in a given range e.g height Discrete = data can only take certain values, e.g shoe size
What is bivariate data?
Data which has pairs of values for two variables
What is the difference between qualitative and quantitative data?
Quantitative = numbers Qualitative = words
What is the name of a line of best fit for a scatter diagram? What is it used to find?
- Regression of y on x
- Can only be used to find y from x, not vice versa
What is the height of a histogram bar?
it’s frequency density
What are the 4 conditions for binomial distribution?
- There are a fixed number of trials
- There are 2 possible outcomes
- There is a fixed probability of ‘success’
- The trials are independent of one another
