## Types of Data

August 28, 2013

For class on Thursday, August 29th

I will present these **PowerPoint slides** covering key material in Chapter 1. Click here to download the slides: ch01** [I may a few edits that can be found here: ch01-jh]**

Here’s a link to a **YouTube video** (6 min) that we will watch in class. The woman narrating the video is from New Zealand so she may be difficult for some to understand. But, hopefully it will be helpful to hear about the same topic presented another way.

There were a couple of helpful questions and answers on the YouTube page

Q1. But what is the difference between interval and ratio data or scale?? In my book they are given separately and i m not able to comprehend the difference between the two 🙁

A1. The difference isn’t usually relevant in statistics, so I didn’t confuse things by adding that level. Ratio data has a meaningful zero value, and ratios of numbers make sense. For example temperature is interval data as the difference between 30 degrees and 40 degrees is the same as the difference between 40 degrees and 50 degrees. However it is not meaningful to say that 40 degrees is twice as hot as 20 degrees. So temperature is not ratio data. Length in mm, is ratio data. 20mm is twice 10mm.

Q2. So basically it’s like this. Nominal data is numbers given to stuff like name Kevin=1 Women=2 but it does not imply order (such as I’m above women). Ordinal data does imply order but the intervals (amount) between the order may not be equal. Interval/Ratio/Scale data is quantitative of the data and gives mean, median, and standard deviation. Correct?

A2. Yup – you got it. Nominal doesn’t always have numbers assigned. It is often left as text.