chapter 16 - data

Question 1

discrete data

Answer 1

unordered or exact values

Question 2

discrete data represented

Answer 2

• ungrouped freq table
• bar chart, line graph, dot plot, pie chart, stem and leaf
• (n+1)/2

Question 3

continuous data

Answer 3

unordered and measured to a better degree of accuracy

Question 4

continuous data represented

Answer 4

• grouped freq table
• histogram or cumulative freq graph
• n/2

Question 5

drawbacks or grouped data

Answer 5

• lose info
• class size arbitrary

Question 6

how to work out quantiles / median of continuous data

Answer 6

use the number line and the fraction of the way in it is

Question 7

histograms equation

Answer 7

freq = class width x relative freq / freq density
(area of histogram bar)

Question 8

standard deviation

Answer 8

measures the mean difference of each data point from the mean
= root (sum of(x-mean)^2) /n)
or = root( sum of(x^2) /n -mean^2)

Question 9

how to do standard deviation on calc

Question 10

variance of (x)

Answer 10

standard deviation^2 = sum of((x-mean)^2) /n

Question 11

what is standard deviation

Answer 11

a measure of the amount of variation or dispersion of a set of values

Question 12

what is variance

Answer 12

the degree of spread in your data set

Question 13

+/- of mean/sd

Answer 13

+ take into account all data unlike IQR which only tells you about the middle half
- outliers can skew the sd/mean and make it not a good representation

Question 14

what to watch out for with groups

Answer 14

undefined intervals - the intervals in the table may not be the actual interval eg when measuring to the nearest cm 10-15 actually means 9.5-15.5

Question 15

correlation

Answer 15

the relationship between bivariate (paired) data

Question 16

interval description set notation

Answer 16

[ = including
( = not including
eg [140-150) includes 140 not 150

Question 17

correlation coefficient

Answer 17

1= strong +
0 = no linear correlation
-1 + strong -
r = +-1 = perfect correlation
represents the correlation

Question 18

two ways to find if a value is an outlier

Answer 18

> 1.5 xIQR from the nearest quartile
2 standard deviations from the mean

Question 19

regression line

Answer 19

line of best fit on a scatter graph

Question 20

extrapolation

Answer 20

using the regression line to predict values outside the range of observed data

Question 21

whether to include outliers

Answer 21

if its clearly an error eg an impossible value - exclude it
- several outliers could indicate a different distinct group