Bivariate Data

NZ Level 6 (NZC) Level 1 (NCEA)

Comparing Sets of Data II (includes box and whisker)

Lesson

It is important to be able to compare data sets because it helps us make conclusions or judgments about the data. For example, say Jim got $\frac{5}{10}$510 in a geography test and $\frac{6}{10}$610 in a history test. Which test did he do better in? Just based on those marks, it makes sense to say he did better in history.

But what about if everyone else in his class got $\frac{4}{10}$410 in geography and $\frac{8}{10}$810 in history? If you had the highest score in the class in geography and the lowest score in the class in history, does it really make sense to say you did better in history?

By comparing the means of central tendency in a data set (that is, the mean, median and mode), as well as measures of spread (range and standard deviation), we can make comparisons between different groups and draw conclusions about our data.

Marge grows two different types of bean plants. She records the number of beans that she picks from each plant for $10$10 days. Her records show:

Plant $A$`A`: $10,4,4,5,7,10,3,3,9,10$10,4,4,5,7,10,3,3,9,10

Plant $B$`B`: $8,7,5,5,9,7,8,7,5,6$8,7,5,5,9,7,8,7,5,6

What is the mean number of beans picked per day for Plant $A$

`A`? Leave your answer to one decimal place if needed.What is the mean number of beans picked per day for Plant $B$

`B`?What is the range for Plant $A$

`A`?What is the range for Plant $B$

`B`?Which plant produces more beans on average?

Plant B

APlant A

BPlant B

APlant A

BWhich plant has a more consistent yield of beans?

Plant A

APlant B

BPlant A

APlant B

B

The residents of two blocks of townhouses were asked the number of pets they own. The frequency of various responses are presented in the dot plots.

According to the data, which of the following statements are true?

Pet ownership is a little lower in block $A$

`A`.True

AFalse

BTrue

AFalse

BIn block $A$

`A`, most households have zero or one pet.True

AFalse

BTrue

AFalse

BIn block $B$

`B`, most households have three or more pets.True

AFalse

BTrue

AFalse

BIn block $A$

`A`, pet ownership is skewed negatively.True

AFalse

BTrue

AFalse

BPet ownership ranges from $0$0 to $3$3 pets in block $A$

`A`.True

AFalse

BTrue

AFalse

BThere is more variability in the block $B$

`B`distribution.True

AFalse

BTrue

AFalse

BBoth sets of scores have an outlier.

True

AFalse

BTrue

AFalse

B

Student X scored $86,83,86,88,98$86,83,86,88,98 and

Student Y scored $61,83,50,85,83$61,83,50,85,83 across 5 exams.

Find the mean score of Student X, writing your answer as a decimal.

Find the mean score of Student Y

Find the standard deviation of the scores for Student X, correct to two decimal places.

Find the standard deviation of the scores for Student Y, correct to two decimal places.

Which student performed better?

Student X

AStudent Y

BStudent X

AStudent Y

B- Which student performed more consistently?
Student X

AStudent Y

BStudent X

AStudent Y

B

Plan and conduct investigations using the statistical enquiry cycle: A justifying the variables and measures used B managing sources of variation, including through the use of random sampling C identifying and communicating features in context (trends, relationships between variables, and differences within and between distributions), using multiple displays D making informal inferences about populations from sample data E justifying findings, using displays and measures.

Investigate a given multivariate data set using the statistical enquiry cycle

Investigate bivariate numerical data using the statistical enquiry cycle