doubt, quesn 6 practice assesment 1 ( not graded)

[niraj gaurav]

Variables with an interval scale of measurement may be converted into a ratio scale of measurement by performing?

 a)Addition operation

 b)Subtraction operation

 c)Multiplication operation

 d)Cannot be converted to ratio variables

how can an interval scale of measurement be converted into ratio scale by subtraction? please explain

[mayur...@gmail.com]

Hi Niraj,

Take an example of temperature measured in degree Celsius. We know the temperature measured in degree Celsius is interval scale of measurement. Take three temperatures as 10 degree, 20 degree and 40 degree. we can not say 20 degree is twice as hot as 10 and same as 40 degree is twice hot as 20.

Now, we will do subtraction operation.

40 - 10 = 30 degree

20 - 10 = 10 degree

Here,  30 degree difference is thrice as hot as 10.

So, the subtraction  operation convert interval scale of measurement into ratio scale of measurement.

I think, this explanation will help you.

Thanks,

Mayur Gundal,

Course content support team,

IITM online degree

[niraj gaurav]

thank you so much, this helps alot.

 i have another doubt.

Can an unstructured data be categorical? 

[niraj gaurav]

@malabika

On Wednesday, October 7, 2020 at 7:15:08 PM UTC+5:30 Malabika Guha Mustafi wrote:

Yes, unstructured data can be categorical ( example: email contents, suggestions etc).

[Malabika Guha Mustafi]

Thanks for clearing the concept. 

[CG]

Hi Mayur and course team,

In your example to Niraj below (40-30=10 and 20-10=10), the unit is still the same even after subtraction - Therefore it would still be wrong to say that 30°C is thrice as hot as 10°C. Please correct this.

However °C can be converted to °K by adding 273.15. (ratio to interval)

and °F can be converted to °K by (x°F − 32) × 5/9 + 273.15 (ratio to interval)

I also noticed that this question is there is practice assignment for week 1 but the it is different in the Practice Assignment Week 1 - Video Solution and Practice Assignment Week 1 - PDF Solution.

Please clarify.

[Statistics 1 Support 1]

Hello, 

Even though the unit is same, since here it is not just temperature measured. It is the difference in temperatures of two points. That 40 C-30 C= 10 C or 10K both are correct. 

Let's say we have 3 bodies at temperature 10C, 20C, and 30C respectively. The difference between third and first body (30C- 10C = 20K or 20C) is twice of difference between second and first body(20C-10C = 10C or 10K).

Thanks & Regards,

Ram,

Course Support Team

[CG]

Thank you Ram and Mayur.

I had misunderstood that doing a subtraction operation would "convert" the temperature to a ratio scale. 

Thank you very much for explaining it. However I have the following doubt.

Consider the following example (spread sheet below) which is a dataset of today's temperature in 13 Indian cities. 

• Column 1 and 2 is the original dataset. 
• Column 3 compares the difference between the temperatures of 2 alphabetically-adjacent cities (sorted in alphabetical order)
• Column 4 compares the difference between the temperature of each city and the mean temperature of the 13 cities.
• Column 5 converts the temperature of the city to Kelvin unit of measurement
• Column 6 converts the temperature of the city to Fahrenheit unit of measurement. 

Now, if we consider the values in column 3 and 4, the computed value no longer represents the temperature of a city. The new variable represents something totally different. Therefore it would be incorrect to call it a "conversion."

Question 6 in Practice Assignment 1 : "Variables with an interval scale of measurement may be converted into a ratio scale of measurement by performing?"

The above question implies that it is the same variable. ie: In the example above, temperature of a city (variable) in °C can be converted to °K by performing an addition operation. The variable storing the temperature in °C and the variable storing the temperature in °K still represent the temperature in a given city. You can generate a new variable (representing difference/comparison) by a subtraction operation.

I appreciate the hard work you are doing to try and clarify the questions of ~30,000 registered participants.

Thank you.

[Nikita Kumari]

Hi,

After conversion of one variable by performing subtraction, it will become a new variable. But this is not a variable which we have recorded. So, the variable obtained by subtraction operation is a new variable but we have converted it from original variable. So saying conversion is not wrong.

Regards,

Mayur,

Course content support,

IITM Online degree

[CG]

The subtraction operation to generate a new variable that no longer represents the property of the original variable would be termed a computation.

 

Calling it a 'conversion' is rather imprecise and introduces ambiguity as I have illustrated in the example above.

To further illustrate the point:

• I can 'compute' or 'calculate' or 'find out' mean or variance or standard deviation or difference between 2 values. Using the word 'convert' here is imprecise.
• I can 'convert' temperature from centigrade to kelvin or length from centimetres to inches.

Hope you understand now.