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Ah I thought this would be a new take on that apocryphal bayesian story >An engineer draws a random sample of electron tubes and measures their voltage. The me
by krackers 4y ago
Ah I thought this would be a new take on that apocryphal bayesian story
>An engineer draws a random sample of electron tubes and measures their voltage. The measurements range from 75 to 99 volts. A statistician computes the sample mean and a confidence interval for the true mean. Later the statistician discovers that the voltmeter reads only as far as 100, so the population appears to be 'censored'. This necessitates a new analysis, if the statistician is orthodox. However, the engineer says he has another meter reading to 1000 volts, which he would have used if any voltage had been over 100. This is a relief to the statistician, because it means the population was effectively uncensored after all. But, the next day the engineer informs the statistician that this second meter was not working at the time of the measuring. The statistician ascertains that the engineer would not have held up the measurements until the meter was fixed, and informs him that new measurements are required. The engineer is astounded. "Next you'll be asking about my oscilloscope".
- unlikelymordant 4y agoCan you explain the story? I understand an oscilloscope is for looking at signals, but i dont understand the significance
- fenomas 4y agoThe context can be found here: > https://en.wikipedia.org/wiki/Likelihood_principle#The_voltmeter_story https://en.wikipedia.org/wiki/Likelihood_principle#The_voltm... Specifically if you read the "Example 2" section above that blurb, and then read the "throwback" bit at the end after the voltmeter story, it makes more sense.
- quickthrower2 4y agoWhat is a good book for someone comfortable with maths (but very out of practice) to get up to speed on the topic. Not being scared of not understanding stuff and needing to learn prerequisites (so doesn’t need to be too easy). Because the wikipedia article isn’t really for learning but it does give a flavour. And it sounds fascinating, sort of like a monte hall problem to me.
- deleted 4y ago[deleted]
- whatshisface 4y agoOscilloscopes can also be used to measure voltages, often in excess of 100V, so in the spirit of those extremely unlikely "explanations" that show up in the explainxkcd tables, I offer this. PS this story doesn't make sense because you can tell when a voltmeter is out of range.
- aix1 4y ago> PS this story doesn't make sense because you can tell when a voltmeter is out of range. It's also a bit sloppy with the bounds. To me, "reads only as far as 100" includes 100V, whereas the measured voltages only go as high as 99V.
- whatshisface 4y agoWhile we're complaining, you can't measure the "voltage" of an electron tube out of circuit.
- ilyt 4y agoSure you can, just buy a SMU (source measurement unit, few multimeters cobbled together with 4 quadrant power supply)
- YetAnotherNick 4y agoI think the point is that the sample readings were in the range of voltmeter, but if some sample crossed 100V it would show as 100V in the voltmeter. So even though no sample crossed 100V, the data is clipped still.
- whatshisface 4y agoThat's not good statistics - just because the precision of measurements falls off sharply at 100V doesn't mean that out-of-range readings aren't valid measurements.
- 4y ago
- charcircuit 4y agoWhy would the population be censored if the voltmeter never read anything above 100 volts?