Stats Exam 2

• ŷ = b_o + b₁ x
• b_o is intercept and b₁ is slope
• find this by using least squares method

• b₁ = ^Sy/S_x  and b₀= Y-bar - b₁x̅  

• difference between the observed value and what the model predicts
• e = y-ŷ  Residual = observed - predicted
• also: y = ŷ + e

Way to model the relationship between two quantitative variables with a line

shows relationship between quantitative variables.

causal variable on the x-axis

• Outlying in X-values
• is influential

• parameter: unknown population quantities
• Statistics computed from a sample are used to estimate parameters which describe a population.

every possible sample of size n has the same chance of being selected

divide area into subareas and then take a simple random sample within those subareas

involves sampling every k^th unit in an ordered list of the units in the population

random sample of clusters of individuals, and then survey every indidual

situations when using more than 1 sampling mehtod

• Nonresponse
• Interviewer Bias - The teacher personally asking students about the class, or only asking certain groups known of having a certain opinion
• Question Wording

• Effect variable
• on the Y-Axis

• The researcher only observes to collect data
• no manipulation

• The response variable is already known
• the explanatory variable is collected by looking at past histories of subjects

Explanatory Variable is observed about subjects, and then they are followed into the future to see response variables

• Researcher assigns the explanatory variable for each unit
• a cause and effect relationship can be established
• if conducted properly the lurking variable can be minimized

in an experiment, a factor is usually a categorical explanatory variable, and the levels are the different possible values

• Necessary: comparison, randomization, Replication
• Other: Placebo, Blindness