WEEK 4 Flashcards
Closed ended questions
Can answer yes or no
Secondary data
Someone else has already collected
Primary data
The one you collect yourself for
S formuła
Squared sum of all ( x - x) ^2 / n-1
Advantage of sampling
Save time and money
Sometimes the only option
Sampling errors (drawbacks)
Bias- whne the sample is not representative of population this bias can be computed and analysed
Non sampling errors - missing data, defective questionnaires etc this cannot be computed and analysed so readily sampling must be planned and carried out well
Sample statistics
x (WOTH the line) mean
S for standard deviation
And p for the n (not n it’s that lol thingy)
CC x SE =
Accuracy
CIT - confidence interval for
Create prediction interval for means ‘ confidence interval’ which gives a good sense of accuracy
SE standard error
S/ N (square rooted n)
How spread out the means of the samples are
Open ended questions
Opinions etc ideas regarding a question
Centrism limit theorem
For population distribution we don’t take into consideration
Methods of sampling
Random
Systematic
Stratified
Cluster
Random sampling
Out of everyone anyone has equal chance of being picked
Systematic sampling
Stratified sampling
Divided population into groups that share common characteristics
Collecting data
Techniques
Observation - counting
experimentation -
Survey/ interview
central limit theory
No matter what the actual population distribution is if you take many large enough sample and calculate the mean of each of those samples those means will follow a normal distribution
This normal distribution has its mean the real population nuu and standard deviation called standard error
SEM
Q / n (square rooted)
SEP
Squared rooted P( 100-P) / n
