Statistics and Data Analysis (Lecture 6)

Question 1

How should you round off?

Answer 1

• Look at all the digits beyond the last place desired.
• Numbers that are more than halfway to the next higher digit are rounded up, and vice versa.
• In the case where the number is exactly halfway, round to the nearest even digit.

Question 2

What is the real rule?

Answer 2

The first digit of absolute uncertainty is the last significant digit in the answer.

Question 3

What is raw data?

Answer 3

Unchanged data acquired directly from the measurement. A copy of raw data should always be kept.

Question 4

What is processed data?

Answer 4

Data which has been subjected to any type of alteration such as data analysis, removal of outliers, removal of noise, etc.

Question 5

How does the normal (Gaussian) distribution link to analytic chemistry?

Answer 5

• Statistics gives us tools to accept conclusions that have a high probability of being correct and to reject conclusions that do not.
• If an experiment is repeated many times and if the errors are purely random, then the results tend to cluster symmetrically about the average value.

Question 6

What is the mean (average)?

Answer 6

The sum of the measured values divided by the number of measurements.

Question 7

What does the standard deviation measure?

Answer 7

How closely the data are clustered about the mean.

The smaller the s.d. the more closely the data are clustered about the mean. And the more precise our measurement is.

Question 8

What is p-hacking or data dredging?

Answer 8

the misuse of data analysis to find patterns in data that can be presented as statistically significant when in fact there is no real underlying effect