Time-Mean Speed is the mean of speeds at one location over time. Which choice best describes this?

Time-Mean Speed is the mean of speeds at one location over time. Which choice best describes this?

• A. Geometric mean of speeds
• B. Harmonic mean of speeds
• C. Maximum speed observed
• D. Mean of all speeds at one location

Answer: (D)

Time-mean speed comes from averaging the speeds observed at a single location over a time interval. Each vehicle’s speed recorded as it passes is treated as one data point, so you add all those speeds and divide by how many observations you have. That is the arithmetic mean, where every observation is weighted equally in time. Geometric and harmonic means describe other kinds of averages that arise in different contexts: the geometric mean deals with multiplicative changes, and the harmonic mean is appropriate when averaging rates over a distance (because time spent depends on speed). Taking the maximum speed is not an average at all, it just selects the fastest value. So the best description is the mean of all speeds observed at one location over time.

Time-mean speed comes from averaging the speeds observed at a single location over a time interval. Each vehicle’s speed recorded as it passes is treated as one data point, so you add all those speeds and divide by how many observations you have. That is the arithmetic mean, where every observation is weighted equally in time.

Geometric and harmonic means describe other kinds of averages that arise in different contexts: the geometric mean deals with multiplicative changes, and the harmonic mean is appropriate when averaging rates over a distance (because time spent depends on speed). Taking the maximum speed is not an average at all, it just selects the fastest value.

So the best description is the mean of all speeds observed at one location over time.