Nayland College

Nayland College - Mathematics

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NZAMT NZQA NZ Grapher NZ Maths Census at School Study It

Cleaning Data

1.11 Bivariate Home | Assessment Criteria | Ask a Question | Make a Plan | Collecting Data | Cleaning Data | Making Scatterplots | Describing Scatterplots | Outliers | Line of Best Fit | Population Inference | Conclusion | Revision

5



Cleaning Data

Checking the data set and how to clean the data

Look for correct recording of data, consistent units, data errors, and zero entries

Any values that do not form a PAIR of variables are removed from the data set.

Is a strange data value an outlier or an incorrect value?

Cleaning data Class notes, Blank notes  

 

“I wonder if there is a relationship between the number of texts sent and time talking on a cell phone for students in year 11 at Nayland College”

 

In last 7 days, Number of:

Gender

Texts sent

Texts Received

Calls made

Calls Relieved

B

14

10

3

6

B

241

183

24

48

B

45

37

30min

45min

B

27

100000

12

8

G

211

317

16

10

G

-17

37

3

9

G

316

426

n/a

0

G

89

95

16

2.4

We ‘clean’ the data by removing individual data values that are errors
These could be typing errors, silly entries, incorrect units eg grams & Kg
Check ‘0’ entries carefully. Is it a zero or  n/a entries

Sometimes more data will be needed to get a sample set of 30 data values

 

 

 

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