ch 2. presenting data Flashcards
frequency distribution defn
• Frequency distribution shows the freq of each meas of a variable (in a table)
relative frequency defn
• Relative frequency- the number of times a partic observation occurs divided by the total number of observations
what would present a bigger picture the relative freq or the freq distibution
freq distribution
cumulative freq defn
• Cumulative frequency lists the number of observations with a value less than the max value of the variable interval see page 15 eg if you have 9 pts discharged on day 3 or earlier the total includes all pts that stayed 0,1,2,3 days added up.
cumulative relative freq
calculated by adding together all the relative freq less than or equal to the selected upper limit point
can make it into % to understand better
grouped freq
• Grouped frequencies are freq distributions with distinct intervals or groups to simplify info.
what is the drawback of using grouped frequencies
Some info is lost this way esp if you use large intervals
cumulative percentage defn
• Cumulative percentage-the % of obs with a value less than the max value of the variable interval (same idea as cumulative freq but in %)
what is a quantile
• Quantiles—two kinds-percentiles and quartiles
quartile
how is a percentile different
(divide a data set into four equal parts with first uartile being the 25th percentile, second quartile is 50th percentile etc)
percentile divides a data set into 100 equal portions
percentile rank
the % of observations lower than that score in a freq distribution
what kind of data does a bar chart show
is it often used when each answer is distinct and in no particular order
• Bar chart-show nominal categorical data. Often used when there are spaces between bars and each answer is distinct and in no partic order
histogram defn
what kind of data are they gen used for
• Histograms are a type of bar chart often w no spaces bet bars as theyre often for continuous or ordinal data
what kind of data are line graphs best for showing
• Line graphs are best for showing continuous variables that change over time
outlier defn
• Outliers are data that are outside the expected relationship
scatterplot
• Scatterplots . each point shows how one subject relates to two variables
what does it mean when points are close together or seem to follow a line closely
the relationship bet variables on horizontal and vertical axes are relatively strong
if scatterplot indicates positive relationship what would this look like
and negative
o When the dots go from bottom left and go up this indicates a positive relationship (as one inc the other inc as well eg ht and wt)
o If they start in upper left and go down towards right then its neg relationship
if charting nominal data what might you use
bar chart
if wanting to graph ordinal or continuous data might use
histogram
to graph continuous variables that change over time might use
scatterplot
