Q&A - PSLE Science

[Dharma]

atutor2001:

Hi everybody


One of my friends asked me why is it necessary to \"repeat an experiment\". Without thinking I regurgitated : \"so that the results will be more reliable, consistent and accurate\".

She told me that her DD's teacher told them that \"accurate\" cannot be used. Another friend also said the same thing. Just curious, is this the latest MOE teaching concept.

I used to teach my kids that \"repeating an experiment\" will make results more accurate because it allows the \"average\" to be computed, which will help to reduce experimental error. Wonder why it is no longer valid. Hope to hear your comments. Thank you.

Hi atutor2001,

I remember from dd’s time in P5/P6, that repeating the experiment/talking more measurement gives more reliable results and not accurate results.

If the action of repeating the experimental steps/taking more measurements help to reduce random error because measurements fluctuate about some value – they are sometimes larger and sometimes smaller. So, by averaging over repeated measurements, the errors will tend to cancel and random error reduces. If random error is small we say the measurements are precise.

For measurements to be accurate, we systematic error must be small. The most common source of a systematic error is an incorrectly calibrated instrument or instruments that have zero error. Here, the observed measured measurement and expected measurement will be different resulting in inaccurate measurement if the instrument is not properly calibrated before use. Here, by repeating the measurements many times will not reduce the systematic error but only random error.

But for PSLE Science, the kids just need to understand that the purpose of repeating the steps of the experiments/ taking more measurements will gives us more reliable results. [JMHO]

[atutor2001]

Dharma:

Hi atutor2001,

I remember from dd’s time in P5/P6, that repeating the experiment/talking more measurement gives more reliable results and not accurate results.

If the action of repeating the experimental steps/taking more measurements help to reduce random error because measurements fluctuate about some value – they are sometimes larger and sometimes smaller. So, by averaging over repeated measurements, the errors will tend to cancel and random error reduces. If random error is small we say the measurements are precise.

For measurements to be accurate, we systematic error must be small. The most common source of a systematic error is an incorrectly calibrated instrument or instruments that have zero error. Here, the observed measured measurement and expected measurement will be different resulting in inaccurate measurement if the instrument is not properly calibrated before use. Here, by repeating the measurements many times will not reduce the systematic error but only random error.

But for PSLE Science, the kids just need to understand that the purpose of repeating the steps of the experiments/ taking more measurements will gives us more reliable results. [JMHO]

Hi Dharma

Thank you for your clarification. I fully agree with your explanation that repeating the experiment will not guarantee that the results will be more accurate - especially if, let say, one of the equipment is faulty.

However, I remembered coming across a question in the PSLE past year Science booklet, a past PSLE question which asked : \"How will repeating an experiment make the results more accurate?\" This question indirectly implies that \"repeating the experiment will make results more accurate\" is true and it is a PSLE question.

Hence, I was wondering if there was a change in MOE's teaching concept with regards to this aspect on experimentation.

Regards

[Dharma]

atutor2001:

Dharma:

Hi atutor2001,

I remember from dd’s time in P5/P6, that repeating the experiment/talking more measurement gives more reliable results and not accurate results.

If the action of repeating the experimental steps/taking more measurements help to reduce random error because measurements fluctuate about some value – they are sometimes larger and sometimes smaller. So, by averaging over repeated measurements, the errors will tend to cancel and random error reduces. If random error is small we say the measurements are precise.

For measurements to be accurate, we systematic error must be small. The most common source of a systematic error is an incorrectly calibrated instrument or instruments that have zero error. Here, the observed measured measurement and expected measurement will be different resulting in inaccurate measurement if the instrument is not properly calibrated before use. Here, by repeating the measurements many times will not reduce the systematic error but only random error.

But for PSLE Science, the kids just need to understand that the purpose of repeating the steps of the experiments/ taking more measurements will gives us more reliable results. [JMHO]

Hi Dharma

Thank you for your clarification. I fully agree with your explanation that repeating the experiment will not guarantee that the results will be more accurate - especially if, let say, one of the equipment is faulty.

However, I remembered coming across a question in the PSLE past year Science booklet, a past PSLE question which asked : \"How will repeating an experiment make the results more accurate?\" This question indirectly implies that \"repeating the experiment will make results more accurate\" is true and it is a PSLE question.

Hence, I was wondering if there was a change in MOE's teaching concept with regards to this aspect on experimentation.

Regards

Hi atutor2001,

You may wish to refer slide 25 of this link from a Science Workshop for Parents 2010
http://www.yewteepri.moe.edu.sg/announcementsDetail.aspx?AutoPk=133&year=2010

[atutor2001]

Thank you Dharma for the site. I guess there is indeed a change in the teaching concept.

[Nebbermind]

while graphite is a known conductor of electricity, is the term ‘carbon’ considered conductor or non-conductor?

[snowman.022851697]

Graphite is carbon molecules arranged in a certain way. Therefore, carbon is an electrical conductor.

[atutor2001]

Nebbermind:

while graphite is a known conductor of electricity, is the term 'carbon' considered conductor or non-conductor?

The safest answer is : \"Some forms of carbon are conductor of electricity\". If it is True or False question, I would put True.

[Nebbermind]

http://img137.imageshack.us/img137/3121/dsc00302f.jpg

this is from this yr's prelim paper. Do you think the lamp will ever light up?

how do one interprete a switch that joins 3 paths?

[Nebbermind]

atutor2001:

Nebbermind:

while graphite is a known conductor of electricity, is the term 'carbon' considered conductor or non-conductor?

The safest answer is : \"Some forms of carbon are conductor of electricity\". If it is True or False question, I would put True.

http://img713.imageshack.us/img713/1037/dsc00303x.jpg

I need P & R to be conductors. So shd it be (3) or (4)??

[atutor2001]

Nebbermind:

atutor2001:

[quote=\"Nebbermind\"]while graphite is a known conductor of electricity, is the term 'carbon' considered conductor or non-conductor?

The safest answer is : \"Some forms of carbon are conductor of electricity\". If it is True or False question, I would put True.

http://img713.imageshack.us/img713/1037/dsc00303x.jpg

I need P & R to be conductors. So shd it be (3) or (4)??[/quote]I will pick (4) because it is the best answer as all forms of pure aluminium and copper are conductors of electricity.

As for carbon, only graphite is a conductor of electricity and other forms of carbon, e.g. diamond, coal, soot, are non-conductor of electricity.

If there is no option (4) than (3) would be the best answer.