BSSE Flashcards
What happens to PPV if disease prevalence increases?
PPV increases
What happens to NPV if disease prevalence increases?
NPV decreases
What happens to NPV if sensitivity increases?
NPV increases
What happens to NPV if sensitivity decreases?
NPV decreases
What happens to PPV if specificity increases?
PPV increases
What happens to PPV if specificity decreases?
PPV decreases
What is the equation for the false positive rate?
false positive / (false positive + true negative)
What is the equation for the false negative rate?
false negative / (false negative + true positive)
What is the equation for sensitivity?
TP/(TP+FN)
What is the equation for specificity?
TN/(TN+FP)
What is the equation for positive predictive value?
TP/(TP+FP)
If disease prevalence increases, PPV increases.
What is the equation for negative predictive value?
TN/(TN+FN)
Sensitive test if negative, will rule the disease out.
What does a specific test indicate if positive?
Will rule the disease in.
What does specific test indicate if negative
Rule disease out
PPV change with disease prevalence increase
PPV increases
What happens to standard deviation if precision increases?
Decreases
What happens to statistical power if precision increases?
Increases
What does sensitivity describe?
Sensitivity describes how well a test can detect a specific disease/condition in people that actually have it.
What does specificity describe?
Specificity describes the percentage of people who test negative for a specific disease among a group of people who do not have the disease.
What is prevalence?
Number of people with an illness at a given time
What is incidence?
Number of new cases at a given time
If the incidence decreases, then prevalence
Decreases
Can independent events be mutually exclusive?
No
What defines two sets as non-mutually exclusive?
They share common elements
What occurs in a type I error?
False positive
What occurs in a type 2 error?
False negative
What is the probability of getting Alpha level (usually 0.05)?
a type 1 error
What is the probability of getting Beta level (often 0.2)?
a type 2 error
What is the equation for power?
1 - beta
What is the fraction of experiments in Power?
which you would expect to find a statistically significant result
What is the equation for power related to positive and negative results?
TP / (TP + FN)
What happens if a type 1 error is made?
Beta will increase
If a type 1 error is made, power will _
Decrease (power=1-beta)
When do you use a t-test?
When you have 2 groups and ONLY 2 groups!
When do you use an ANOVA?
When you have three or more means.
Central tendency is another term for…
Mean
How are the mean, median and mode related in a normal distribution?
Mean=median=mode
In a normal distribution, what is the 95% confidence interval in terms of standard deviation?
2 SD
In a normal distribution, what is the 99% confidence interval in terms of standard deviation?
2.5 SD
What is the equation for standard deviation?
sqrt of variance
Why do we subtract 1 from the variance?
Lowers population, more conservative error value
What is a positive skew?
More scores fall in the lower range, so the curve will have a positive skew when plotted.
What is a negative skew?
More scores fall in the higher range, so the curve will have a negative skew when plotted.
In a positive skew, how are mean, median, and mode related?
Mean > median > mode
In a negative skew, how are mean, median, and mode related?
Mode > median > mean
What kind of data is categorical?
Nominal, dichotomous, and ordinal.
What is nominal data?
Examples include bungalow, condo, house.
What is dichotomous data?
Examples include male/female.
What is ordinal data?
Examples include not very much, a lot, etc.
What type of data is continuous?
Interval and ratio.
What is an example of interval data?
Temperature.
For what data is mode the best measure of central tendency?
Nominal.
When is mean the best measure of central tendency?
When data is continuous.
What measure of central tendency is used for ordinal data?
Mode and median.
What measure of central tendency is used for interval and ratio data?
Mean, median, or mode.
How do you calculate SEM?
SD/square root of the sample set
A 99% confidence interval is _ than a 95%.
Less precise
A 99% confidence interval is _ than a 95%.
More Accurate
What test is used for categorical data?
Chi square
What test is used for continuous data?
T-test or Analysis of Variance (ANOVA)
When do you use a Fisher’s exact test?
When comparing proportions of two categories
