Terms in this set (24)
What is the difference between a statistic and a parameter?
Parameter describes the population and statistic describes the sample
What is the sampling distribution of a statistic?
the distribution of values taken by the statistic in all possible samples of the same size from the same population
What does it mean for an estimator to be unbiased?
An unbiased estimator is an accurate statistic that's used to approximate a population parameter.
standard error of estimate
a measure of variability around the regression line - its standard deviation
How do we interpret a confidence interval?
We say that a C% confidence interval means that C% of all samples will capture the true value. That means that we are C% confident that the interval includes the true value.
What happens to the interval as the confidence level or the sample size increases?
Higher the confidence interval, wider the interval. As the sample size increases, the interval gets smaller.
the hypothesis that there is no significant difference between specified populations, any observed difference being due to sampling or experimental error.
Type I error (alpha)
False positive results
ex: reject the null hypothesis when you should accept it
What is the p-value of a test and how is it interpreted?
p-value represents the significance of the results of a test
How do we graphically check whether a data set is drawn from a normal distribution?
QQPlot, should follow a 45 degree line. Normal Probability Plot, should form a linear line. Histogram (normal distribution)
What is the criterion for fitting a regression equation?
Assumptions for regression: The Two Variables Should be in a Linear Relationship, All the Variables Should be Multivariate Normal, No multicollinearity, Equal variance, and no autocorrelation
How do we interpret R-squared in a regression context?
R-squared is a statistical measure of how close the data are to the fitted regression line
What is the difference in the objective when estimating the mean response at a particular x-value versus predicting a response at that x-value?
What is multicollinearity and how does it affect inference in a regression problem?
Multicollinearity is a statistical phenomenon in which multiple independent variables show high correlation between each other. In other words, the variables used to predict the independent one are too inter-related.
What is the purpose of blocking in an experimental setting?
blocking is the arranging of experimental units in groups (blocks) that are similar to one another.
What are the advantages of replication in an experiment?
A replication experiment is performed to estimate the imprecision or random error of the analytical method
What are the advantages of randomization of treatments to experimental units?
Using randomization in an experiment can establish a cause and effect relationship. Under random assignment the groups shouldn't differ significantly with respect to potential lurking variables. Experiments with randomization of treatments establish a clearer causal relationship and it controls for all lurking variables
Why are placebos used in medical experiments?
Used as a control group and placebos are most commonly used in blinded trials, where subjects do not know whether they are receiving real or placebo treatment.
What does correlation measure?
the degree of relationship between two or more variables
How are correlation and causation related?
Causation explicitly applies to cases where action A causes outcome B. Correlation is simply a relationship.
What is the nature and purpose of ANOVA?
used to determine whether there are any statistically significant differences between the means of three or more independent (unrelated) groups
Type II error (beta)
False negative results
ex: accept the null hypothesis when you should reject it
margin of error estimate
a statistical figure, based on sample size for a poll, that indicates where the true value in the population probably lies
The hypothesis stating what the researcher is seeking evidence of. A statement of inequality. It can be written looking for the difference or change in one direction from the null hypothesis or both.
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