Biostatistics

Question 1

What is continuous data?

Answer 1

numerical data in which the magnitude from one value to the next is equal (HR, age, height, degrees C and F)

Question 2

What is discrete/categorical data?

Answer 2

1. Nominal- arbitrary order (gender, mortality, ethnicity, marital status)
2. Ordinal- logical order but magnitude from one value to the next is not equal (1-10 pain scale, NYHA functional class

Question 3

What are measures of central tendency?

Answer 3

a typical value that describes all the possible values and likelihoods that a random variable can take in a given range:
1. mean
2. median
3. mode

Question 4

What is mean and when is it preferred?

Answer 4

1. average value
   2.continuous data that is normally distributed

Question 5

What is median and when is it preferred?

Answer 5

1. middle value
2. ordinal or continuous data that is skewed

Question 6

What is mode and when is it preferred?

Answer 6

1. most frequent value
2. nominal data

Question 7

How is the variability of data (spread) described?

Answer 7

1. range
2. standard deviation

Question 8

What is the range?

Answer 8

difference between the highest and lowest values

Question 9

What is standard deviation?

Answer 9

indicates how spread out the data is and to what degree the data is dispersed away from the mean (highly dispersed data have a larger SD)

Question 10

What are the characteristics of Gaussian (normal) distribution?

Answer 10

1. large sets of continuous data
2. normal/symmetrical bell-shaped curve
3. mean, median, and mode are the same value at the center point of the curve
4. 68% of data fall within 1 SD of the mean; 95% of data fall within 2 SD of the mean
5. half of the values are on the right and the other half on the left with a small number of data in the tails

Question 11

What are the characteristics of a skewed distribution?

Answer 11

1. not symmetrical
2. data is skewed toward outliers (extreme high value is skewed right and extreme lows are skewed left)
3. 68% of values do not fall within 1 SD of the mean, median, and mode
4. mean, median and mode are not the same value
5. usually occurs when the number of values (sample size) is small and/or there are outliers

Question 12

What are the characteristics of outliers?

Answer 12

1. in a small population outliers have a large effect on the mean
2. median is a better measure of central tendency
3. distortion from outlier is decreased by increasing the population

Question 13

What is a variable?

Answer 13

any data point that can be measured or counted

Question 14

What is an independent variable?

Answer 14

variable that is changed (manipulated) by the researcher to determine its effect on the dependent variable (the outcome)

Question 15

What are examples of dependent variables?

Answer 15

1. A1c
2. cholesterol values
3. mortality
   the outcome of an independent variable

Question 16

What are examples of independent variables?

Answer 16

1. drug/dose regimen
2. patients included (age,gender, comorbid conditions)

Question 17

What is a null hypothesis?

Answer 17

Ho: hypothesis that the researcher is trying to disprove or reject (drug X does not treat HF better than drug y); not statistically significant difference

Question 18

What is an alternative hypothesis?

Answer 18

Ha: hypothesis researcher is trying to prove or accept ( drug x treats HF better than drug y); statistically significant

Question 19

What is the alpha level?

Answer 19

standard for maximum permissible error margin and threshold for rejecting the null hypothesis; usually 0.05 (5%)

Question 20

What is a p-value?

Answer 20

calculated based on statistical test data and compared to alpha; when the p-value is < 0.05 the results are statistically significant and the null hypothesis is rejected

Question 21

What is a confidence interval?

Answer 21

1. includes data on statistical significance and precision of results
2. CI= 1- alpha
3. when alpha is 0.05 the study reports a 95% confidence interval
4. when alpha is 0.01 the study reports a 99% CI