what is validity?reliabily?and accuracy? (1 Viewer)

[evil99]

anyone out there? help me please

I did an experiment where we have to measure the heating effect of current pass through the conductors
what are the access of validity of the conclution?
what are the justify reliabity and accyracy of the experiment?

 

[kini mini]

When you are analysying your results to fraw a conclusion from an experiment, you must consider how those results could have been affected by the process you used. For example, let's say you were doing a titration and you only did it once. You would then have doubts about the reliability and accuracy of your results since you didn't repeat the experiment. Therefore, any conclusion you drew from those results might not be valid.

 

[Twintip]

Accuracy relates to how close you are to the theoretical value. It is affected by scale of your equipment (eg: measuring out 25mL in a pipette is much more accurate than measuring out 25mL in a measuring cylinder), among other things. In the titration example above I don't think it'd be possible to comment on accuracy just on that result alone. You would need to compare with other experiments and any theoretical calculations to work out how accurate you were.

(Edit: Crap, forgot this was the physics forum!)

Reliability is concerned with the consistency of results. Reliable results can still be inaccurate if, for example, one part of your apparatus isn't right (eg: a galvanometer isnt calibrated correctly). To conduct a reliable experiment, all except the one variable must be controlled. This means you use the same galvanometer for each test. You repeat the experiment and from these repeated tests you average them to gain a result more reliable than any one test on its own (this eliminates any outliers too, like if you accidentally read a wrong value in one test or something).

These two factors combine to determine how valid your results are. Your repeated experiments must show a consistency of results (reliability) while at the same time being correct in the sense that they are accurate to within x% of the theoretical value (if you don't know this, you just need to make sure your equipment is in perfect working order, etc).

 

[Constip8edSkunk]

assessment of procedure and the minimizations of variables also count in validity doesnt it?

 

[+:: $i[Q]u3 ::+]

Originally posted by Constip8edSkunk
assessment of procedure and the minimizations of variables also count in validity doesnt it?

the validity is basically how well your experiement relates to the hypothesis or the problem. If you're testing current, you wouldn't use a voltmeter.

assessment procedure, minimisation of variables all have to do with the reliability of results. How good your experiment is (any error goes here. eg. loss of heat or whatever

accuracy is how correct your measurements are.
if your results are reliable and valid, then they should be accurate, right? Wrong! within reliability, there may be errors of measurement (your voltmeter screwed up, or it's calibrated wrong) These are really difficult to pick up, and they can affect the accuracy of your results.

 

[Constip8edSkunk]

oh ok then, thanks for clearing that up... always had trouble distinguishing btween and writing bout reliabilty/validity

 

[airman 2]

Validity!

Validity

In general validity refers to whether the measurements you are taking are cause by the phenomena you are interested in. For the validity of conclusion, data and information gathered from secondary source from the internet website were valid by checking publisher name, dates publish, named of the source and date updated. This is to ensure that data is valid, thus prevent retrieving data from the wrong or out of date web site eg: (ghost website). Information can be confidence in validity by first of all, start to read simple text book to get the fundamental knowledge about the subject, with fundamental knowledge we can valid by which source of data in the internet are useful and related to our, thus information would not be easily fool by unprofessional webmaster, student can determine whether the information is useful or not by question themself whether the information they are finding is related to the hypothesis.
With the first hand investigation for validity of the results you should use high sensitive heat measuring device like data logger probe, however the disadvantage is that, it is expensive and are not available at school. The variable and control must keep in mind to valid, but sometime human errors have limited the ability to keep accurate results. Also instead of using water, we could replace liquid Nitrogens. But it would not be possible due to safety and economic issues. Liquid Nitrogen are expensive and can only use by well train professional, because of it extreme low temperature (-170C) if it contact with skin, it cause cold burn, initially vapour can effect by breathing
Consequently, it can be seen that to validity of the conductions from gathered data and information has arise an issues of economic, human errors and safety, the validity of the conclusion could minimise by comparing secondary sources or other group, however in first hand investigation technology is limit in finding accurate and valid conclusion.

 

[airman 2]

Reliability and accuracy

Generally speaking reliability is concerned with the consistency of results and accuracy is how correct measurements are. It is effect by scale of equipments, for example results would not be accurate because in some galvanometer and ammeter, the needle scale positions a little shift away from the zero line, this need to be carefully screw and adjust to zero mark for an accurate measurement. With Copper wires, because it is a very good conductors, the potential different between the metal is low, hence we can not measure accurately by the standard voltmeter. For a more reliable and accurate results, a Cathode Ray Oscilloscope (CRO) is needed to replace a voltmeter. However CRO has complex characteristic and can be function correctly if know how to use, hence learning how to operated CRO need time and effort to practice, in addition because copper produce less resistance there are minor change in temperature, thus a standard thermometer could not be sensitive enough to detect change in temperature. We would replace a digital thermometer like data logger to make an accuracy measurement, however this equipment is not available from practical room supply, data logger also expensive to buy and must obey safety procedure when operate them. For a results to be reliable make sure that all equipments must keep and constant and obey all the control procedure in each test to minimise the chance of getting inaccurate results. Always repeat the experiment and from these repeat each test, then average them out to gain more reliable results. With timing, because human reaction to trigger their muscle in their body may slow or fast, always use the index finger for accurate timing, and if possible for a greater accuracy, use atomic stop watch, or for cheaper option with three stop watch allow three members in a group to do timing, then get the average of the change in time, thus eliminated any accidentally read wrong value ok

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