Acute exposure to cadmium produces respiratory distress, kidney and liver damage, and may result in death. For this reason, the level of airborne cadmium dust and cadmium oxide fume in the air is monitored. This level is measured in milligrams cadmium per cubic meter of air. A sample of 35 readings yields these data: (Based on a report in Environmental Management, September 1981, p. 414.)

(a) Construct a stem-and-leaf diagram for these data. Use the numbers 02, 03, 04, 05, 06, and 07 as stems.

(b) Would you be surprised to hear someone claim that the random variable X, the cadmium level in the air, is normally distributed? Explain.

(c) Use the method outlined in this section to break these data into six categories. (Here a unit is 1/1000 and a half unit is .0005.)

(d) Construct a frequency table and a relative frequency histogram for these data. Does the histogram exhibit the bell shape characteristic of a normal density?

(e) Construct a cumulative frequency table and a relative cumulative frequency ogive for these data. Use the ogive to approximate that point above which 50% of the readings should fall.