After Taizhou Mei Lanfang Park opened, many people visited it. At a certain time of day in mid-May, we randomly surveyed some visitors to the park and counted them.

(1) Fill in the sample survey or spot check;

(2) ∵a=1-0.200-0.250-0.125-0.075=0.350;

b= 8÷0.200×0.125=5;

c=8÷0.200=40;

The frequency distribution histogram is as shown in the figure.

(3) According to the question, among the number of people surveyed, there are 8+14+10=32 people who waited less than 40 minutes;

Therefore Fill in 32．

(4) ∵The total number of people is 40,

∴The time period where the median is located is 20~30.

So fill in 20, 30.

(1) Due to the large number of people visiting the park, we randomly surveyed some tourists entering the park at a certain time in mid-May and counted the time they spent waiting to check in before entering the park. From this we can Determine the survey method;

(2) First, the total number of people surveyed c can be found based on a known set of data, and then b can be found by multiplying by the frequency. The sum of all frequencies is 1, that is a can be calculated, and then the frequency distribution histogram can be completed;

(3) According to the table, it is known that among the people surveyed, the waiting time is less than 40 minutes, including the first, second and third groups. Use the table The number of people waiting less than 40 minutes can be calculated from the data;

(4) Since we know that the total number of people is 40, we can know which group the median falls on based on the definition of the median.