Reliability
the degree to which the tool measures the same thing each time it is used

Validity
the degree to which the test measures what it is supposed to measure


I know this seems dumb, but after reading my management notes, I really can't grasp the difference between the two of these

for what subject is this?

Management II

Sorry don't know anything about this topic

Got you covered!


Reliability
the degree to which the tool measures the same thing each time it is used

AKA - You measure a stick. The first time around, it measure 10 cm. You measure it again; this time, it measures 10.1 cm. And one more time it measures 10 cm. It is a reliable instrument.

Now let's say you measure a stick and the first time it measures 10 cm. then you measure it again, but this time it measures 9 cm. And again, and it measures 11 cm. And again and suddenly it's, like, 9.5. That instrument is very unreliable, because you can't depend on it to make the same measurement twice.

A better real-life application for this might be a bathroom scale that's super super old (but created recently). You get on it and it reads one thing, then step off and right back on and it reads something completely different - you can't trust it. It's unreliable.
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Validity
the degree to which the test measures what it is supposed to measure

AKA - Say you're measuring that stick again with your tape measure, and you get some good measurements - it seems reliable. However, when you measure the stick with a ruler, it's completely different. The Validity of your instrument would be how close those marks come to the real thing - what it's supposed to measure.

so, say that this is how big a real centimeter is:
|____|

and this is what your instrument reads as a centimeter:
|________|

Your instrument is InValid. It has low validity.

Leave it to Kyralih, the master of everything

Hope that helps you Saturn!

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Reliability
the degree to which the tool measures the same thing each time it is used

How often something will measure or always produce the same result.

If you were testing the boiling temperature of water by measuring it with a thermometer the test should be very reliable and give you the same result each time.

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Validity
the degree to which the test measures what it is supposed to measure

How good was the test at measuring what you were were testing for.

If you were testing to see how fast a piece of card board falls when you throw it out the window and you set it on fire your test didn't have much validity.

I gotta give credit to the boyfriend on this one because i couldn't think of a way to explain it so I asked him to. xD

oh wow. Kyra, you were doing it at the same time. XD

Small Lady wrote:

If you were testing to see how fast a piece of card board falls when you throw it out the window and you set it on fire your test didn't have much validity.

LMAO. FULL WIN.

lol my boyfriend's so funny. if only he didn't not like sailor moon, i'd get him to join. xD