The National Oceanographic and Atmospheric Association (NOAA) has provided data for global temperature changes (rounded to the nearest tenth of a degree C) from the 20th century average temperature of 13.9C. The temperature changes are given with the number of years in two separate frequency tables below.

Table 1 Table 2

20 Years from 1901 - 1920 20 Years from 2001-2020

C change	Frequency (# years)		C change	Frequency (# years)
-0.5	1	0.5	1
-0.4	7	0.6	9
-0.3	7	0.7	4
-0.2	3	0.8	1
-0.1	2	0.9	3
0.0	0	1.0	2

1. Find a weighted mean for theC changefrom the data in the first table, 1901 through 1920, by multiplying theC changeamount by the frequency, then totaling theresults forTable 1 and dividing by the total number of years,20, for the first table.You now have a weighted mean change for Table 1.

2. In the same way, compute the weighted mean for theC changefrom the Table 2 data, dividing the total by the 20 years from 2001 to 2020.

3. Add the mean change from each table to the baseline temperature - the 20^thcentury average of 13.9 C. You will have two centigrade temperatures - a mean temperature from the first half of the 20^thcentury, and one from the last 50 years (excluding the year 2005).

4. Convert each Celsius temperature to Fahrenheit using the formula F = 1.8C + 32

1. State your conclusions regarding the change in the average global temperature between the first half of the 20th century and the last 50 years.