A group of male workers between the ages of 20 and 39 years are being screened for lung disease by spirometry. Nine subjects are examined. Their forced expiratory volume in 1 second (FEV1) divided by forced vital capacity (FEV1/ FVC %) results are 80, 76, 73, 61, 64, 79, 64, 64, and 78. What is the modal reading?
Answer(s): B
The modal reading is the most frequently occurring observation in a group of data. (On a graph of frequency of different observations, this would be where the peak is.) This reading generally is not very useful for statistical calculations, and when the series is small, no modal reading may even occur. When drawn in graph form, the determination of unimodal or bimodal distribution may be a helpful concept from which conclusions may be drawn. The distribution in the example that accompanies the question is unimodal.
A group of male workers between the ages of 20 and 39 years are being screened for lung disease by spirometry. Nine subjects are examined. Their forced expiratory volume in 1 second (FEV1) divided by forced vital capacity (FEV1/ FVC %) results are 80, 76, 73, 61, 64, 79, 64, 64, and 78. What is the median value?
Answer(s): D
The median is the observation that lies in the middle of the series, if the observations are tabulated in numerical order. Half of the observations are lower in numerical value than the median, and the remainder are higher. Clearly, this value is easily identified if the series contains an odd number of readings. Although not very frequently used as a statistic, the median has the advantage of not being affected by extreme observations. For example, if the lowest reading of those in the question had been 55 instead of 61, the median would be unchanged.
A group of male workers between the ages of 20 and 39 years are being screened for lung disease by spirometry. Nine subjects are examined. Their forced expiratory volume in 1 second (FEV1) divided by forced vital capacity (FEV1/ FVC %) results are 80, 76, 73, 61, 64, 79, 64, 64, and 78. What is the range?
Answer(s): C
The range is the difference between the highest and lowest readings in a group of observations. The lowest reading is subtracted from the highest. Only one of these two readings is included in the range. If both were to be included, the range would be 20, as there are 20 possible values included in the limits of the data presented in the question. For simplicity, the first method is generally accepted. One disadvantage of the concept of range is that it may increase as the number of observations increases.
A group of male workers between the ages of 20 and 39 years are being screened for lung disease by spirometry. Nine subjects are examined. Their forced expiratory volume in 1 second (FEV1) divided by forced vital capacity (FEV1/ FVC %) results are 80, 76, 73, 61, 64, 79, 64, 64, and 78. The variance of the set of values is 58.75.What is the standard deviation (SD)?
The variance is the sum of the squares of the difference of each reading from the mean. This is a mathematical way of eliminating the opposing effects of negative and positive values. But the variance has a result that is of a different order than the original observations. The variance of 58.75 seems to have little relationship to a series of readings from 61 to 80. In order to determine a value that is the same order as the observations, the SD is calculated as the square root of the variance. This is mathematically represented as:Without using a calculator, it can be seen that the nearest correct answer (correct to 1 decimal place) is 7.7.
The crude death rate in Sweden was 0.010 per year, while in Costa Rica it was 0.008 per year. All age- specific death rates, except those for the oldest-age category, were higher in Costa Rica than in Sweden. From these data, one can correctly infer which of the following?
In a crude death rate, all deaths are in the numerator, and the total midyear population in the denominator.In age-specific death rates, the calculation is done using data from specific age intervals. Small differences in crude death rates may enable specific deductions to be made. Ahigher death rate in the older population may indicate that a more fragile population has successfully survived to that age. Of the statements listed, considering that age-specific death rates were greater in all age groups except the elderly, only the fact that a greater proportion of the population in Sweden is in the older age groups could account for the difference in crude mortality rate.
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