statistical inference
what we know so far
inference
the process of drawing conclusions based on findings from statistical tests
how the inference works in research using statistics
1. collect data
2. data analysis
3. inference about findings
Steps
1. determine point estimate
2. calculate confidence intervals
point estimate
a single number used to estimate the population parameter for confidence intervals
What is the best estimate of population mean??
the sample mean
-we use this single number to calculate the confidence interval
confidence intervals
for the mean specify an interval of values
-our goal is to see if we can estimate a range of numbers from sample data that we can make conclusions about a population
rules
also called assumptions
rules for CI
-normal distribution on bell curve
-interval/ratio (continuous) data required for raw scores
samples less than 60
use critical values for t
samples greater than or equal to 60
use critical values for z
standard error equation
SE = standard deviation / square root of sample size
conclusion statement
______ times (either 95 or 99) out of 100 the mean (insert VARIABLE of interest) will be between _____ and ______.
small standard error
more accurate point estimate thus better chance the population mean is actually close to your sample
large standard error
less accurate point estimate thus a lower chance that the population mean is close to the sample mean