摘要：Revision: Histograms Histograms are similar to bar charts apart from the consideration of areas. In a bar chart, all of the bars are the same width and the only thing that matters is the height of the bar. In a histogram, the area is the important thing. Example Draw a histogram for the following information. (Ignore relative frequency for now). It is difficult to draw a bar chart for this information, because the class divisions for the height a
Revision: Histograms
Histograms are similar to bar charts apart from the consideration of areas. In a bar chart, all of the bars are the same width and the only thing that matters is the height of the bar. In a histogram, the area is the important thing.
Example
Draw a histogram for the following information.
……
(Ignore relative frequency for now). It is difficult to draw a bar chart for this information, because the class divisions for the height are not the same. The height is grouped 0-2, 2-4 etc, but not all of the groups are the same size. For example the 4-5 group is smaller than the 0-2 group.
When drawing a histogram, the y-axis is labeled 'relative frequency' or 'frequency density'. You must work out the relative frequency before you can draw a histogram. To do this, first you must choose a standard width of the groups. Some of the heights are grouped into 2s (0-2, 2-4, 6-8) and some into 1s (4-5, 5-6). Most are 2s, so we shall call the standard width 2. To make the areas match, we must double the values for frequency which have a class division of 1 (since 1 is half of 2). Therefore the figures in the 4-5 and the 5-6 columns must be doubled. If any of the class divisions were 4 (for example if there was a 8-12 group), these figures would be halved. This is because the area of this 'bar' will be twice the standard width of 2 unless we half the frequency.
A-level课程优势：
· 课程体系：全程服务，20-32小时集训拔高，80小时自主学习与督导指点我们陪你每一分钟
· 课程资料：1）CIE、Edexcel官方教材；2）独家考前押题秘籍；3）2015-2017年考试真题模考精讲；
· 无忧备考：名师授课+作业批改与点评+ 期中、期末模考精讲+24小时答疑+一直到考前也会进行的伴读计划
· 明星师资：授课老师均毕业于美国TOP30名校和国内985名校，IELTS考分8+，同时教授过至少3000个小时的课程
· 教学方法：超过同类机构两倍的刷题量、考前预测各个击破讲练并进，问答结合，真正掌握每一个知识点
针对2018年的A-level考试，开设“A-level基础课程、强化课程、冲刺课程”。想快速提分的同学可以在线咨询客服，了解课程详情，预约名师1V1试听课；为你量身打造专属A-level学习方案；免费领取A-level考试学习资料/视频课件/直播公开课！