Data Presentation and Analysis

Data Presentation and Analysis: Anomalies and Experimental Errors

Mrs. Simmonds-Gordon

Lesson Objectives

• At the end of this lesson you should be able to:

• identify and explain experimental errors

• Construct results tables

• Construct pie charts using results from observations or other sources of data

Anomalies

• Definition: RESULTS THAT DO NOT FIT WITH THE GENERAL PATTERN.

• Caused by experimental errors

• These errors occur when the recorded reading is different from what it is supposed to be (true value).

Example of Anomalous Data

A farmer with a large mango orchard hired some workers to assist with picking the mangoes from his trees. The following are the data he collected over the space of a week. See if you can find the anomaly.

Monday: 2 workers ---- 10 mangoes

Tuesday: 4 workers ---- 20 mangoes

Wednesday: 6 workers --- 30 mangoes

Thursday: 8 workers --- 4 mangoes

Friday: 10 workers --- 50 mangoes

WRITE DOWN YOUR ANSWER. A QUESTION IS COMING.

Multiple Choice

On which day was the anomalous data recorded?

• Monday

• Tuesday

• Wednesday

• Thursday

• Friday

TAKE ANOTHER LOOK AT THE DATA

A farmer with a large mango orchard hired some workers to assist with picking the mangoes from his trees. The following are the data he collected over the space of a week. See if you can find the anomaly.

Monday: 2 workers ---- 10 mangoes

Tuesday: 4 workers ---- 20 mangoes

Wednesday: 6 workers --- 30 mangoes

Thursday: 8 workers --- 4 mangoes

Friday: 10 workers --- 50 mangoes

Multiple Choice

What is the expected number of mangoes for Thursday?

• 60

• 4

• 40

• 6

What should you do with/about anomalous data?

• Do not ignore it
• Try to figure out what went wrong and where.
• Remember to be honest! Your "error" may be a new discovery.

Home work: Read about how Roy Plunkett invented Teflon®.

Types of Experimental Errors

• Systematic errors

• Random Errors

• Human Errors

Systematic Errors

These errors are usually caused by repeating the same error throughout the experiment. The error is usually due to taking measurement with faulty or inaccurate instruments. Some faults with instruments that may lead to this are:

1. poor calibration - the instruments have not been adjusted and tested to ensure that they give accurate readings. Eg. a scale that does not go to 0 when not in use.
2. damage or overuse: Eg. if the spring in a scale is worn out, it will stretch much lower in response to weight and give an incorrect reading
3. parallax: when an instrument is read from a bad angle. Eg. reading an analogue clock from the side rather than from the front.

Multiple Choice

Teacher said to measure and cut a piece of string that was 10 cm long. When all the strings were compared, Dahlia's was much shorter than all the others? What could have caused this?

• parallax

• damaged or overused instrument

• poor or no calibration of instrument

Parallax - Dahlia did not read her ruler correctly. Maybe she read it from a bad angle.

Random Error

These errors occur due to changes in environmental conditions that the experimenter cannot change or control and is usually unaware of. Though these changes may be very small, they are significant enough to affect measurements taken during an experiment.

Eg. a 1 degree change in the temperature of the air outside

Random Error continued

Random errors may also come about by making estimations during measurements.

Eg. Trying to measure between the millimetre marks on a ruler

How to minimise random errors

This can be done by repeating your experiment at least 3 times and taking the average of readings or measurements that you take.

Human Error

There a myriad (many, many) such errors. This can range from not following the experimental procedure or method correctly to writing down a wrong number or word.

eg. missing a step or substituting/improvising recording the wrong data not using instruments correctly many others...

Can you think of any?

Thank you for your attention.

Head on over to Google Classroom for your activity.

BYE!! :)