Interpreting Data Flashcards
Types of quantitative data
Discrete
Continuous
Types of qualitative data
Nominal
Ordinal
What is the difference between nominal and ordinal date
Nominal unordered, ordinal ordered
2 measures of location
Median
Mean
2 measures of spread
Standard deviation
Interquartile range
Standard deviation
quantity expressing by how much the members of a group differ from the mean value for the group
Average squared distance form mean, squared
When should median and interquartile range be used instead of mean and standard deviation
When sample has outliers
What is the term for distribution of many random variables as a symmetrical bell-shaped graph
Gaussian distribution (normal distribution)
How does the number of values within any specified number of standard deviations above or below the mean vary with sample size in a Gaussian distribution
No change
What percentage of values lies within 1.64 standard deviations of the mean in a Gaussian distribution
90%
How many standard deviations above or below the mean do 95% of the values in a Gaussian distribution lie
1.96
Standard error what does standard error measure
Statistical accuracy of an estimate
Standard error of the mean
Standard deviation of the distribution of all possible sample means
What does a 95% confidence interval mean
We are 95% sure the true value lies within a certain range
What is the most commonly used confidence interval
95%
How does the 95% range size change as sample size increases
Stays the same
How does confidence interval change as sample size increases
Narrows
What is the correlation between 2 variables when r= 1, 0, and -1
1 - perfect positive correlation
0 - no correlation
-1 - perfect negative correlation
What distribution of data is spearman’s rank used on
Non linear mono tonic relationship - non Gaussian
What does spearman’s rank assess
how well the relationship between two variables can be described using a monotonic function
What is used to calculate spearman’s rank
Difference in ranks between 2 ranked datasets
Regression curves
Linear
Quadratic
Cubic
Exponential growth
Exponential decay
Sigmoid
What can be used to determine if an observed difference is due to chance
Confidence intervals
P values
What does p value assess
how likely you are to have found a particular set of observations if the null hypothesis were true
Degrees of freedom
Number of values free to vary
When can t tests be used
When 2 measurements are made on the same group
Can t tests be performed on non Gaussian distributions
No - non Parametric test used instead
When should a fishers exact test be used instead of chi squared test
Sparse data
What do chi squared tests assess
Difference in actual data from predicted results
