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Average is a fine measure. You've inferred that they used a mean average. The article doesn't say what kind of average they took. Let's assume they did take a
by chrisbroadfoot 14y ago
Average is a fine measure. You've inferred that they used a mean average. The article doesn't say what kind of average they took.
Let's assume they did take a mean. If the mean error for 1700 devices was 24 minutes, the total error is 40,800 minutes. That's 28 days.
Therefore, they didn't include the outlier of 42 years in their average. It's most likely a median (or mode) average.
- blahedo 14y agoIt's pretty unlikely to be a median; if 20% of machines are 30 minutes off and 24 minutes is a median, then 30% of machines are between 24-30 minutes off, which would seem to be a strangely narrow band. More likely, the 24 minutes is a mean average after excluding outliers. One of the standard ways to compute outliers is to measure the inter-quartile range---the "distance" between the 25th percentile value and the 75th percentile value---and call everything that is more than 1.5*IQR past the 75th percentile an outlier. You can do this without computing a mean first, and you can use it to exclude values before computing a modified mean.