SURFing with Statistics New Zealand

Nathaniel Pihama and Deborah Brunning

Statistics New Zealand

Statistics Teachers' Day30 November 2007

What you will see today

• SURF for Schools

• The Statistics New Zealand website

• Table Builder

..and some ideas on how to use them!

The First SURF: a Synthetic Unit Record File for Schools

Overview:

• Confidentiality – Big Picture

• SURF???– What is it?– How and why did we make a SURF?

• What teachers and students can do with the SURF

What is a Unit Record File?

Other names• Data set• Unit Record Data set• Microdata

Example: A Dataset:Name Gender No.Sibs Age;yrsAmy F 1 14Ben M 2 13Cher F 1 15

Confidentiality

Safe

UnsafeUseless Useful

The pocket

Raw dataset

Non release

Confidentialised Unit Record Files

Confidentiality methods include:Categorical Data• Global recoding• Local recoding

• Numerical Data • top/bottom coding, • capping,• rounding,

Before Top and Bottom Coding

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Salary: k$/yr

FreqAfter Top and Bottom Coding

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Salary: k$/yr

Freq

What is the SURF?

• Data from 200 synthetic respondents.

• Target population is those aged 15-45 in paid employment.

• 7 variables

personid gender

qualification age hours income marital ethnicity

1 female school 15 4 87 never european

2 female vocational 40 42 596 married european

3 male none 38 40 497 married maori

4 female vocational 34 8 299 never european

5 female school 45 16 301 married european

6 male degree 45 50 1614 married european

7 female none 36 12 201 other european

What does the SURF look like?

The first 7 of 200 complete unit records

SURF- the variables

How to start SURFing?• The gender gap (Level 3 and 4)

» Do more females have higher qualifications than males?

» Is this different from how it was in the past?

• Am I average? (Level 4) » What defines the average person?

• Under pressure? (Level 5)» Are people who have never been married different

from married people?

• Equal Pay! (Level 6) » Are males and females paid equally?

• Money for nothing (Level 7) » Investigating hours worked by employees in a

company• Should I do a degree? (Level 8)

» Investigation into whether getting a degree helps improve earning power

http://www.stats.govt.nz/schools-corner

• A large company is concerned that it has too many employees who do not work a 40-hour week.

• You have been hired to investigate the working patterns of the employees.

Task -Money for Nothing

Further Analysis- Hours by Gender

SURF CURF

Related variables – Hours by Marital Status

SURF CURF

Related variables – Hours by Age GroupSURF CURF

How ‘school friendly’ is SURF????

• SURF Excel spreadsheet

• Records are in random order – First 30 records could be used for manual

data analysis

• Use ExcelHow???????

Add Age_10 variable

Add random numbers (then paste special as values)

An example of how to take a stratified sample

Use filter – copy and paste records

Sort on random numbers

Filter function

Pivot Tables

Pivot Tables

Box plots !!!!

QUARTILE functionSORT by Marital

Regression and Residuals• Trend line in a scatter plot

– Good for quick visual check

– Provides equation & R-sq

– But no residuals

• Plot the data (XY scatter)

(tidy plot up)

• Add TrendlineChart menu > Add trendline

Options tab

y = 17.058x + 0.3487

R2 = 0.6323

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Regression and Residuals

• Using Excel functions

– SLOPE(), INTERCEPT(), RSQ()

Copy cell ref into formula bar

Regression and Residuals- Easy to create predicted values and residuals

(can copy formula and use $)

Regression and Residuals- Plot the residuals

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The Statistics New Zealand Website

Stats NZ Products and Services• Schools Corner

– Full of resources based on the curriculum.

• Information releases – Hot Off the Press – Full of highlights, commentary, technical notes and tables!

• New Zealand in Profile– Quick stats of New Zealand for 2007

• Analytical reports– Contain in depth analysis, background and technical

information

• Table Builder– Customisable tables of released survey data

Stats NZ Products and Services• Schools Corner

– Full of resources based on the curriculum.

• Information releases – Hot Off the Press – Full of highlights, commentary, technical notes and tables!

• New Zealand in Profile– Quick stats of New Zealand for 2007

• Analytical reports– Contain in depth analysis, background and technical

information

• Table Builder– Customisable tables of released survey data

Stats NZ Products and Services• Schools Corner

– Full of resources based on the curriculum.

• Information releases – Hot Off the Press – Full of highlights, commentary, technical notes and tables!

• New Zealand in Profile– Quick stats of New Zealand for 2007

• Analytical reports– Contain in depth analysis, background and technical

information

• Table Builder– Customisable tables of released survey data

Stats NZ Products and Services• Schools Corner

– Full of resources based on the curriculum.

• Information releases – Hot Off the Press – Full of highlights, commentary, technical notes and tables!

• New Zealand in Profile– Quick stats of New Zealand for 2007

• Analytical reports– Contain in depth analysis, background and technical

information

• Table Builder– Customisable tables of released survey data

Battle for the ‘greener suburb’:

an example of using case data from Table Builder

• Problem – the statement of the research questions

• Plan – planning the procedures used to carry out the study

• Data – the data collection process

• Analysis – the summaries and analyses of the data to answer the questions posed

• Conclusion – the conclusions about what has been learned.

The statistical investigation cycle:(Wild and Pfannkuch, 1999)

Battle for the ‘greener suburb’:an example of using case data

• Comparing the ‘traveling to work’ habits of area units within Auckland.

• Which area has the ‘greener’ workers?– Walking / Running / Cycling

– Public transport

– Carpooling?

– Working at home?

Battle for the ‘greener suburb’:where to find the data

• We want a data source that contains information about modes of travel to work by area units.

• Luckily, we have the 2006 Census of Population and Dwellings on Table Builder!

   

• So this is some of what Statistics New Zealand has to offer for teachers.

• Do you know about: – Statzing?– CensusAtSchool?– Statistics and Research?