Chapter 8 Flashcards
We use sample data to…
Estimate properties/characteristics of the population.
Sample statistics are used to…
Estimate population parameters.
Point estimate
The value of a sample statistic that is used to estimate a population parameter.
Interval estimation
An interval is constructed around the point estimate.
It is stated that this interval contains the corresponding population parameter with a certain “confidence level”.
Types of estimation
- Point
- Interval
Confidence interval
An interval, calculated from sample data, that is likely to contain the true population parameter with a certain level of confidence.
Confidence interval margin of error
Confidence intervals provide an estimate along with a margin of error, reflecting uncertainty.
Wider interval = more uncertainty
Narrower interval = more precise estimate
Representative as half the confidence interval.
Point estimate for a population mean…
Will always be the sample mean
Confidence level for population mean scenarios
Scenario 1: population standard deviation is known and either n > 30 or the population is approx. Normal.
Scenario 2: the population SD is not known and either n > 30 or the population is approx. Normal.
Alpha
The significance level
Z-value gives each tail a probability of a/2
Alpha = 1 - confidence level
Ex: 98 % confidence level = 0.02 = alpha
Width of a confidence interval
Margin of error (E)
Degrees of freedom
When trying to find a t value
N-1
T distribution
Bell-shaped distribution with a lower height and a greater spread than the standard normal.
As sample size becomes larger, the t distribution…
Approaches standard normal distribution
Point estimate for population proportion
Will always be the sample proportion.
Uses z-value.
