 
 <translate> When Joe added 20% more data points to the dataset, the data points in the dataset increased by 20 / 100 * 200 = 40 data points. The total number of data points increased to 200 + 40 = 240. If he reduced the data points by 1 / 4 of the total data points, the data points reduced by 1 / 4 * 240 = 60. The total number of data points left in the dataset after Joe reduced the data points by 1 / 4 of the total data points is 240 - 60 = 180.
Thus, the answer is 180. <hau> Lokacin da Joe ya kara 20% ƙarin bayanan bayanai zuwa bayanan bayanan, bayanan bayanan da ke cikin bayanan sun karu da 20 / 100 * 200 = 40 bayanan bayanai. Adadin adadin bayanai ya karu zuwa 200 + 40 = 240. Idan ya rage bayanan bayanai ta hanyar 1 / 4 na dukkanin bayanan bayanai, bayanan bayanan da aka rage ta hanyar 1 / 4 * 240 = 60. Jimlar adadin bayanan da aka bari a cikin bayanan bayan Joe ya rage bayanan bayanan ta 1 / 4 na jimlar bayanan bayanai shine 240 - 60 = 180. Saboda haka, amsar ita ce 180. 