Summary Statistics
What is the term for the middle value of a data set?
Median
What is a study that asks questions of a sample drawn from some population in the hope of learning something about the entire population?
a sample survey.
What is a percentile?
A measure that indicates the value equal and below for which a given percentage of observations fall.
What do you describe when asked to describe a scatterplot?
Direction, Outliers, Form, and Strength (DOFS)
What is the formula for calculating the sample mean of a data set?
Sum of all data points divided by the number of data points
A sample is said to be _________ if the statistics computed from it accurately reflect the corresponding population parameters.
representative
In this type of study, participants are randomly assigned to treatments.
Completely randomize experiments
What does a z-score measure?
The number of standard deviations a data point is from the mean.
What is the distance from the predicted value to the actual value called?
A residual
What statistic measures the spread of data around the mean?
Standard Deviation
A sample design in which entire groups are chosen at random.
A cluster sample
When participants in an experiment are similar and organized in homogeneous groups
Blocking
What percentage of the data falls within one standard deviation of the mean in a normal distribution?
68%
Describe what the correlation coefficient tells us.
Indicates the direction (positive or negative) and the strength of the relationship that may exist for a given set of data points.
What is the difference between the range and the interquartile range (IQR)?
The range is the difference between the highest and lowest values, while IQR is the range of the middle 50% of the data (Q3 - Q1)
This sample consists of individuals who are easily available.
A convenience sample
An individual is not aware of how subjects have been allocated to treatment groups.
blinding
If a data set is normally distributed, what percentage of the data falls within three standard deviations of the mean?
99.7%
How do you know whether a linear regression is appropriate?
The scatterplot is roughly linear and the residual plot shows no pattern.
What is the 5 number summary?
Minimum, Q1, Median, Q3, and Maximum
This occurs when some groups in the population are left out of the sample and leads to under-representation.
Undercoverage
A treatment known to have no effect.
A placebo
How do you calculate a Z-score?
Z = (X - mean)/standard deviation
What does LSRL stand for?
Least-squares regression line