This is the stuff you need to make sure you understand this lesson:
- Stem-and-leaf plots (stemplots):
- A stemplot is another useful way of summarising a small to medium sized set of data.
- Each number in a set of data is broken into two parts; the right-most digit becomes a leaf, and all the other digits become a stem.
- Check out WE 14oon textbook page 40 to see how this is done
- When creating a stemplot make sure you:
- end up with 5 to 10 stems - split stems into a smaller class interval if needed (see half way down page 41 for an explanation)
- evenly space the leafs
- put leafs in numerical order
- use a key
- Since the stemplot is in numerical order the Q1, median, Q3 and IQR can be easily found - check out WE 16oon textbook page 42.
- Stemplots look like a Histogram on it's side.
NOW do your 1F exercises.
- Box plots:
- A boxplot is a 'picture' of the minimum, Q1, median, Q3 and maximum values of a set of data (see example above - minimum=30, Q1=52, median=76, Q3=102, maximum=125).
- The minimum, Q1, median, Q3 and maximum are called the five-number summary of a set of data. The five-number-summary is always is this order (min,Q1,med,Q3,max).
- A boxplot is always drawn with an evenly spaced scale, counting by 2 or 5 or 10 or 100 or whatever is best.
- Outliers (extreme values) are values in the data that don't 'seem' to fit, or are exceptional (see "Identification of extreme values" on page 47
- To describe the distribution (of the data values), you must write something about the shape, the centre, and the spread of the boxplot or histogram.
- minimum to Q1 and
- Q1 to median and
- median to Q3 and
- Q3 to maximum
- Also note how a boxplot and histogram are matched.
Now do your 1G exercises.
No comments:
Post a Comment