Homework1_solution

# Homework1_solution - Homework 1 example solution and...

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Homework 1 example solution and marking guide Raw data: Table of reaction times in ms for 50 measurements, made at 2:30pm, Friday 10 th September 2010 using the ‘Reaction’ program. 389 288 368 289 348 261 261 276 271 295 376 339 274 285 322 270 295 300 279 258 264 250 267 292 251 255 326 349 284 284 303 303 255 237 368 622 245 256 236 225 294 288 279 197 289 269 254 222 266 255 The data plotted in histogram format using PhysPlot Mean: 291 ± 9 ms (evaluated by PhysPlot) Standard Deviation = 62.7 ± 6.2 ms (evaluated by PhysPlot) Variance = σ 2 = 3931 ms 2 Median = 279 ms

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Mode = 220 ms Range = 622-197 = 425 ms Chosen binning: 20 bins in range 150-650, bin width = 25ms The histogram is not symmetric and slightly skewed to shorter reaction times (the median < mean, skew = mean-mode/ σ = 1.13) with some outliers at long reaction times, which can be attributed to a lapse in concentration. We would expect the distribution to be Gaussian in shape if a large number of
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Unformatted text preview: measurements were taken and the method truly sampled just my reaction time. However, it was noted that it is possible to cheat – for example by holding the mouse button down and just releasing it when the lights change, or by trying to pre-empt the change since reactions before the change are not recorded. This could explain the skew to shorter reaction times. Marking scheme out of a total of [20] At least 50 data points [1] Description of conditions in which data was taken [2] Histogram Suitable binning [1] Axes labels [2] Units for reaction time [1] Plot title or figure caption [1] Correct Mean and quoted correctly with units[2] Correct Error on the Mean and quoted correctly with units [2] Correct Standard Deviation and quoted correctly with units [2] Correct Variance with units[1] Correct Median [1] Correct Mode [1] Quoted result and sensible discussion [3]...
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