Reliability, accuracy, validity (1 Viewer)

[iStudent]

Hi all,

Under which category, (reliability, accuracy, validity) do these fall under?

1. ensuring high precision through repetition. (when I googled precision it defined it as accurate?)
2. removing the outlier
3. drawing a line of best fit
4. minimising experimental error

I'm confused because textbooks don't really explain these clearly...
And I think there are those that could fall under multiple categories... so confusing
Any help is appreciated!

 

[Cleavage]

I'm a pretty shotty chemistry student, but this is how I would classify;

1. Reliability
2. Reliability
3. Reliability
4. Validity

 

[someth1ng]

1. ensuring high precision through repetition. (when I googled precision it defined it as accurate?)
2. removing the outlier
3. drawing a line of best fit
4. minimising experimental error

1. Reliability
2. Validity, reliability, accuracy (all of them are related to this)
3. Stupid question - not really related to any of them.
4. Accuracy

Don't worry about this, it's a stupid question - pretty bad to see in a textbook.

 

[iStudent]

Thank you!

I actually got this bit from a past paper's sample answer (forgot which one) and it was quite confusing.
Also, it's interesting to see how different everyone's answers were...

Here it is anyways: (from an AAS question)
Explain how the method used by the analytical chemist in determining the amount of ions in the dietary tablets ensures accurate and reliable results are obtained (2 marks)

Reliability:
Four different sample solutions are prepared and analysed. This process of repetition ensures reliable results are obtained. The reliability for the analysis of the unknown was high since it was repeated several times and consistent results were obtained, that is, the analysis had a high reliability because it had high precision.
Accuracy:
Three of the four results (samples A,B and D) have been used in determining the average absorbances as the absorbance for sample C is significantly different to the absorbances for samples A, B and D. Using the concordant results is a method of ensuring accuracy.
Accuracy + reliability:
Preparing a number of standard solutions and recording their absorbances allows a graph with a line of best fit to be drawn. This graphical technique accounts for some experimental errors and additionally ensures an accurate and reliable result is obtained.

Also, can someone please explain how they arrived at the above? Thanks. (For the past, I've always though reliability = repetition. Accuracy = apparatus, sig figs. Validity = Controlling variables. I need to revise my definitions )

 

[SuchSmallHands]

Reliability: their answer fits with your definition (repitition)
Accuracy: accuracy actually refers to how close an obtained measurement is to the true or accepted value using (as you have said) the most sensitive equipment available. By removing an outlier this person has ensured their value is close as possible to the true value.
Both: in drawing a line of best fit the impact of minor devoations from the true result is lessened. The results are therefore more repeatable by others and closer to the accepted value. Basically, this allows them smooth out very minor errors that are significant enough to be considered 'outliers' per se.

Your definition for validity is correct, basically, is the only thing that could affect the dependant variable the independent variable? All of your definitions weren't really off, you just need to practice applying the definitions. Some of that sample answer included some different approaches to the nature of reliability and accuracy, which is probably why the markers liked it so much they set it as the benchmark, so don't worry if they seem a little left of centre to you at first.