Studied by 21 people
What are the indices of central tendency used to describe the typical or central value in a distribution?
Mean, Median, Mode
Why are central tendency measures useful in veterinary medicine?
Help you understand & critically evaluate the medical research literature
Understand your patients’ values in relation to the larger population
Understand biological variability
What is the (sum of the observations / # of observations)?
Mean
What is the level below (or above) half of the observations fall (50 percentile)?
Median
How do you calculate Median?
Arrange your #s in numerical order
Count how many #s you have
Odd # - find # in middle / Even # - average with 2 #s in middle
What is the most frequent occurrence of observations?
Mode
T or F: You can have more than one mode.
True
What is it called when you have 2 modes?
Bimodal
What is it called when you have 3 modes?
Trimodal
What is the average value?
Mean
What is the middle value?
Median
What is the most common value?
Mode
What is the notation for population mean?
“mu” = μ
What is the notation for population standard deviation (sd)?
“sigma” = σ
What is the notation for population variance?
“sigma squared” = σ²
How will a Negatively skewed Distribution on a Bell Curve appear?
Curve on the right and tail going to the left
How will a Positively skewed Distribution on a Bell Curve appear?
Curve to the left and tail going to the right
How will a Normal Distribution appear?
No skew - Normal Bell Curve - A perfectly symmetrical distribution
What type of Distribution is seen in the following graph?
What type of Distribution is seen in the following graph?
What type of Distribution is seen in the following graph?
When is it better to use median vs. mean? Why?
For skewed data - Outliers can greatly skew the mean
What is the skew in the direction of?
The tail of the curve
What is the numerical expression of the likelihood of occurrence?
Probability (Pr)
How can Probability (Pr) be expressed?
Fractions
Decimal Fractions
Percent
What type of Probability (Pr) is associated with the likelihood of 1 event occurring?
Simple Probability
What type of Probability (Pr) is associated with looking at 2 events occurring in relation to one another - it looks at the probability of a second event occurring based on the probability of the first event occurring?
Conditional Probability
What is used to calculate the probabilities of independent events?
Complex Probabilities (Multiplication and Addition Rules)
What are we looking to answer in regards to the probability of 2 types of events?
1st when both events occur (A and B)
2nd when either event occurs (A or B)
What are those events whose occurrence is NOT dependent on any other event and can occur at the same time as the other event?
Independent Events
What are events that cannot occur at the same time?
Mutually Exclusive Events
What is used to calculate the probability of independent events BOTH occurring (A and B)?
Multiplication Rule
What is the formula for the Multiplication Rule?
Pr (A and B) = Pr (A) x Pr (B)
What is used to calculate the probability of independent events EITHER occurring (A or B)?
Addition Rule
What is the formula for the Addition Rule?
Pr (A or B) = Pr (A) + Pr (B)
When can both rules occur at the same time?
When NOT mutually exclusive
What is the population to which it might be possible to extrapolate results from a study?
Target Population
What is the population from which the study subjects are drawn?
Study/Source Population
What are available and we are able to sample?
Sampling Frame
What consists of the individuals (animals or groups of animals) that end up in the study?
Sample
What is the collection of individuals, items or measurements that we want to study and make inferences about?
Target Population
What is the goal of designing a study?
To accurately reflect your population of interest
What are all measurements susceptible to?
Error
What are the 2 types of measurement errors?
Random Error (Imprecision)
Systematic Error (Bias)
What type of error is a sampling error?
A form of systematic error
What is a bias in which a sample is collected in such a way that some members of the intended population have a lower or higher sampling probability than others?
Sampling Error
What are the following examples of?
Self-selection Bias
Survivorship Bias
Healthy Worker Bias
T or F: Systematic bias can be reduced through random sampling.
True
What is a selection process that gives each member of the population being studied an equal chance to be chosen?
Random Sampling
What are the 4 types of random sampling?
Simple Random Sample
Systematic Sample
Stratified Sample
Cluster Sample
What is random sampling an attempt to do?
To replicate the characteristics of the Target Populating using a sample
What does NOT guarantee a replication of Target Population characteristics?
Unbiased random sampling
What is the variability of a sample statistic or a random error?
Standard Error of Measurement
What are sources of variation associated with standard error of measurement (random error)?
Natural Variations (ex. morning vs. night)
Imprecise Instruments
Individual Differences (ex. subjective pain rating)
What do Confidence Intervals (CI) surround point estimate with?
Margin of Error
T or F: a 95% CI for a mean has a 95% chance of capturing the “true” mean.
True
What quantifies precision of estimate?
Confidence Interval (CI) Width
What do Confidence Intervals address?
Random Error only
What is a measure of the degree of reliability of a confidence interval?
Confidence Level
Confidence Level is denoted as 100(1-α)%, where α usually equals what?
0.1, 0.05 or 0.01
What are the most frequently used confidence levels?
90%, 95% and 99%
What does a confidence level of 95% imply?
That 95% of all samples would include the true value of the parameter estimated
The higher the ________ ________, the more strongly we believe that the true value of the parameter being estimated lies within the interval.
Confidence Level
Note
Flashcard