5 ms·

That's why it's called an estimation.

by doe88 14y ago

arrrg 14y ago
Shouldn’t the estimation be conservative, not generous? Especially in this case?
- deleted 14y ago
  [deleted]
  - lutusp 14y ago
    The reason for this is that the range estimator can't predict things the driver might do to spoil the forecast, like run the heater, or drive faster than the speed the estimator uses for its assumptions, or engage in urban stop-and-go driving -- all of which Broder did. This is not to suggest wrongdoing, only that the assumptions were overly optimistic. > Estimation theory is an established field, and this is the most basic type of problem. All estimations in this class must make assumptions about future behavior. Changes in behavior change the estimate.
    - freyr 14y ago
      Sorry, I didn't realize anybody had responded when I deleted my post. > The reason for this is that the range estimator can't predict things the driver might do to spoil the forecast Notice that all of the lines are extremely linear, meaning that Broder's behavior (or a miscalibration) caused a consistent bias in the estimate -- for 500 miles! It's very possible to design an estimator that can take this into consideration and make more accurate predictions. > All estimations in this class must make assumptions about future behavior. Changes in behavior change the estimate. Obviously. So what assumptions is it making? "My estimate has been consistently off for the last 250 miles, but it's going to be correct in the next 250 miles.... I can just feel it!" > Changes in behavior change the estimate. They should, but apparently they don't in this case.
- freyr 14y ago
  It's possible that the estimation is accurate/generous when there is plenty of charge left, and conservative when there is little charge left. This would explain why the car didn't actually die when the range estimate hit zero. They may make the estimate conservative when there is little charge left so people are more apt to charge up.
  - LnxPrgr3 14y ago
    For what it's worth, my car's fuel gauge appears to do exactly this—no change from full for the first 60-100 miles, and about 2.5 gallons left on "empty." The first quarter tank lasts a good deal longer than the third, at least according to the gauge. You'd think you wouldn't want to do this with a range estimation because the error's more obvious, but I'm also sure they don't want to sandbag its estimate from a full charge because people will be wondering why they're not seeing the advertised range. I'm sure they do want the car to be able to keep going a little past empty, though, and those spare miles have to come from somewhere.

That's why it's called an estimation.

by doe88 14y ago

That's why it's called an estimation.

arrrg 14y ago

Shouldn’t the estimation be conservative, not generous? Especially in this case?

deleted 14y ago
[deleted]
- lutusp 14y ago
  The reason for this is that the range estimator can't predict things the driver might do to spoil the forecast, like run the heater, or drive faster than the speed the estimator uses for its assumptions, or engage in urban stop-and-go driving -- all of which Broder did. This is not to suggest wrongdoing, only that the assumptions were overly optimistic. > Estimation theory is an established field, and this is the most basic type of problem. All estimations in this class must make assumptions about future behavior. Changes in behavior change the estimate.
  - freyr 14y ago
    Sorry, I didn't realize anybody had responded when I deleted my post. > The reason for this is that the range estimator can't predict things the driver might do to spoil the forecast Notice that all of the lines are extremely linear, meaning that Broder's behavior (or a miscalibration) caused a consistent bias in the estimate -- for 500 miles! It's very possible to design an estimator that can take this into consideration and make more accurate predictions. > All estimations in this class must make assumptions about future behavior. Changes in behavior change the estimate. Obviously. So what assumptions is it making? "My estimate has been consistently off for the last 250 miles, but it's going to be correct in the next 250 miles.... I can just feel it!" > Changes in behavior change the estimate. They should, but apparently they don't in this case.
freyr 14y ago
It's possible that the estimation is accurate/generous when there is plenty of charge left, and conservative when there is little charge left. This would explain why the car didn't actually die when the range estimate hit zero. They may make the estimate conservative when there is little charge left so people are more apt to charge up.
- LnxPrgr3 14y ago
  For what it's worth, my car's fuel gauge appears to do exactly this—no change from full for the first 60-100 miles, and about 2.5 gallons left on "empty." The first quarter tank lasts a good deal longer than the third, at least according to the gauge. You'd think you wouldn't want to do this with a range estimation because the error's more obvious, but I'm also sure they don't want to sandbag its estimate from a full charge because people will be wondering why they're not seeing the advertised range. I'm sure they do want the car to be able to keep going a little past empty, though, and those spare miles have to come from somewhere.