fundamental skills lecture 3- statistic 1 Flashcards
what is a variable?
a unit of data collection whose value can vary
what are factors?
anything with a sex value such as sex, diet and temperature
what are covariates?
quantitative values such as rainfall, concentration and density etc
what is continuous values?
measured data can have infinite values within a range
what is discrete values?
observations can only exist at limited values often counts
what is the difference between nominal and ordinal?
nominal is unordered descriptions and ordinal is ordered descriptions
what is the median?
the value in the middle. if in the middle then find difference between the mean then divide by 2
when do you use the mean and when do you use the median?
the mean is used if a variable is normally distributed and the graph is symmetric. the median is used when its not normally distributed such as the data is skewed to the right
what is the range?
the spread of data or the distance between highest and the lowest
how to identify the interquartile ranges?
divided into 4 quarters. the median is down the middle then 25% each way is the other lines of the box. the interquartile range keeps 50% of observations around the median
what graph and test do you use if your questions whether 2 covariates vary together?
a scatterplot and a correlation analysis
what graph and test do you use for if the question is about causality between 2 covariates?
a scatterplot with a general linear model
what graph and test do you use for if one factor has an effect on another variable that is a factor?
a box plot and general linear model
what graph and test do you use for association between one factor variable with levels of another factor variable?
a bar plot and a chi square test
what graph and test do you use for finding if the mean is statistically different from another mean?
a box plot and a t-test, if they are paired then a paired t-test
