In recent years, haze weather has occurred in many parts of our country, affecting people's travel, work and health. Its formation is related to PM2.5. PM2.5 refers to the atmosphere

Analysis: (I) The sample data drawn from City A are 32, 33, 34, 46, 62, 69 respectively.

The sample data drawn from City B are 34, 38 respectively. , 51, 61, 63, 71,

.xA＝32+33+34+46+62+696＝46, .xB＝34+38+51+61+63+716＝ 53;

Because .xA <.xB,

So the air quality in City A is better.

(Ⅱ) According to the stem and leaf diagram, 3 out of 6 days in City A, the air quality level was Level 1, and 3 days the air quality level was Level 2.

Air quality The data for three days with level one are a1, a2, a3, and the data for three days with air quality level two are b1, b2, b3.

Then all situations where two days are extracted from six days are: : a1a2, a1a3, a1b1, a1b2, a1b3, a2a3, a2b1, a2b2, a2b3, a3b1, a3b2, a3b3, b1b2, b1b3, b2b3.

That is, the total number of basic events is 15;?

Record "exactly one day when the air quality level is Level 1" as event A,

then event A contains The basic events are: a1b1, a1b2, a1b3, a2b1, a2b2, a2b3, a3b1, a3b2, a3b3,

That is, the number of events included in event A is 9;

So P(A )=915=35,

That is, the probability that the air quality level is Level 1 on exactly one day is 35.