(20 14? In recent years, smog weather has appeared in many places in China, which has affected people's travel, work and health. Its formation is related to PM2.5

(1) The sample data of a market are 32, 34, 45, 56, 63 and 70 respectively;

The sample data of city B is 33, 46, 47, 565, 438+0, 64, 765, 438+0.

. x A = 32+34+45+56+63+706 = 50，

x B = 33+46+47+5 1+64+7 16 = 52。

∵.x A

The air quality in cities is better.

(2) According to the stem leaf diagram,

There are two days out of six days in a city where the air quality level is Grade I,

For four days, the air quality level was Grade II.

The four-day data of air quality level II are A, B, C, D,

The two-day data of air quality level I are m, n,

So the situation of taking two days out of all six days is

Ab, ac, ad, am, an, bc, bd, bm, bn, cd, cm, cn, dm, dn, mn, and the total number of basic events is 15.

I still remember "One day the air quality level was Grade 1" as event A,

Then the basic events contained in event a are: am, bm, cm, dm, an, bn, cn, dn,

The number of events is 8.

∴P(A)=8 15.

In other words, the probability that the air quality grade is 1 grade on a certain day is 8 15.