Estimation

Question 1

What are confidence intervals and why are they useful?

Answer 1

Used to quantify uncertainty when taking samples from populations.
A confidence interval gives a range of values which capture the population mean with a given probability.

Question 2

What is a population?

Answer 2

Population is any collection of individuals (or measurements made on those individuals) in which we are interested

Question 3

Define the term sample:

Answer 3

A sample is any subset of a population. It is selected to be representative of the population

Question 4

Define the term random sample:

Answer 4

A random sample is one chosen in such a way that each member of the population has the same chance of selection

Question 5

Define the term population distribution:

Answer 5

The frequency distribution of a variable in the population

Question 6

Define population parameter:

Answer 6

Numerical values that describe characteristics of an entire population.

Question 7

Describe the difference between population parameters and sample statistics:

Answer 7

Population parameter refers to characteristics of an entire population whereas sample statistics refers to characteristics derived from a sample

Question 8

Define accuracy:

Answer 8

How close samples are to the mean (target)

Question 9

Define precision:

Answer 9

How close samples are together

Question 10

Define the sampling distribution of a statistic

Answer 10

Is the frequency distribution of that statistic over all possible samples of a given size selected from the population

Question 11

Define standard error and its use:

Answer 11

The standard deviation of the sampling distribution of a statistic
Used to calculate confidence intervals.

Question 12

What are 2 general properties that affect 95% confidence limits?

Answer 12

The larger the sample size the narrower the confidence interval.
The higher the probability the wider the confidence interval.

Question 13

How do you calculate a confidence interval ?

Answer 13

estimate +/- M X standard error of estimate

where M is a multiplier which depends upon the sampling distribution of the estimate and the percentage used

Question 14

What is the multiplier for a 95% confidence limit and why ?

Answer 14

1.96
Because 95% of a Normal distribution lies within 1.96 standard deviations of the mea

Question 15

How do you calculate confidence interval on SPSS ?

Answer 15

Enter the values of the variable in a column Analyse>Compare means >One Sample T test
Move the variable of interest into Test Variable