Ch 3 stats Flashcards
Why may an outlier be acceptable?
It may be due to the natural variation in the population or a freak of nature.
What are the features of a box plot?
Centre line= median (Q2)
Left line on box= lower quartile (Q1)
Right line on box (Q3).
Far right line is max value
Far left line is min value.
Cross is an anomaly.
What is an important thing to remember when drawing a box plot?
Always give box plot a title.
What is the first thing to look at when you see tabulated data?
Are there gaps between the intervals?
Do I need to think about cum frequency.
What is an important feature of a cumulative frequency graph?
Always connect the start of the graph to the lowest value in the table.
What is the formula related to histograms?
CW x FD = Frequency
What is an important feature of histograms?
The area of the bar is PROPORTIONAL to frequency in each class.
What needs to happen when comparing data?
You compare a measure of location and a measure of spread.
What are the two pairs that you can compare data with?
- Standard deviation and mean.
- Or median and IQR
When comparing data when would you use each pair?
If the data set contains extreme values then the median and IQR are more suitable.
When calculating standard deviation from frequency tables how would you go about it?
Square the values THEN multiply by frequency.
Sigma fx^2, Sigma fx and frequency.
When drawing out a cumulative frequency diagram with tabulated data how do you plot the points?
Take the upper boundary of each interval.
When would a histogram be a suitable method to represent data?
When you are dealing with grouped continuous data.
How can you make a frequency polygon using a histogram?
Join the midpoint top of each bar.
How can you compare two box blots?
Compare the IQR and the median.
