h*********g
发帖数: 18 | 1 I have 2 groups of data, e.g. group one is 1,2,1,3,4, group two is 45,46,56,
34,40. I want to calculate the ratio (group two/group one). I will take the
means of the two groups and calculate the ratio. How do I get the SEM or SD
of the ratios? Thanks. | s******s
发帖数: 13035 | 2 你那两组是啥东西，不说具体，没人知道你想干啥。
如果只是误差的传递的话， 定义f(x) = （误差(x)/mean(x)) ^2
z ＝ x/y , f(z) = f(x) + f(y)
56,
the
SD
【在 h*********g 的大作中提到】
: I have 2 groups of data, e.g. group one is 1,2,1,3,4, group two is 45,46,56,
: 34,40. I want to calculate the ratio (group two/group one). I will take the
: means of the two groups and calculate the ratio. How do I get the SEM or SD
: of the ratios? Thanks.
| h*********g
发帖数: 18 | 3 I only want to get the ratio of group2 to group1. But I need to present the
data as ratio +or- SD(orSEM). I cannot give a single ratio without SD or SEM
. What I mean is that I get an average of group 1 and average of group2,
then get the ratio. But how do I calculate the SD or SEM of the ratio?
Thanks.
【在 s******s 的大作中提到】
: 你那两组是啥东西，不说具体，没人知道你想干啥。
: 如果只是误差的传递的话， 定义f(x) = （误差(x)/mean(x)) ^2
: z ＝ x/y , f(z) = f(x) + f(y)
:
: 56,
: the
: SD
| s******s
发帖数: 13035 | 4 这样说把，理论上，你测量的每组数据是应该一样的么？（比如对同一样品的测量），
如果是，那么估计你关心的是误差，就按照我前面的公式。如果每组都是random
variable，那是没有公式的
the
SEM
【在 h*********g 的大作中提到】
: I only want to get the ratio of group2 to group1. But I need to present the
: data as ratio +or- SD(orSEM). I cannot give a single ratio without SD or SEM
: . What I mean is that I get an average of group 1 and average of group2,
: then get the ratio. But how do I calculate the SD or SEM of the ratio?
: Thanks.
| m*********D
发帖数: 1727 | 5 哈哈，这是生物里统计没好好学的人的方法：
先把group 1的平均数搞好，再那group 2的每个数字除group 1的平均数，得到一组倍
数。然后在算SD/SEM.
56,
the
SD
【在 h*********g 的大作中提到】
: I have 2 groups of data, e.g. group one is 1,2,1,3,4, group two is 45,46,56,
: 34,40. I want to calculate the ratio (group two/group one). I will take the
: means of the two groups and calculate the ratio. How do I get the SEM or SD
: of the ratios? Thanks.
| d***r
发帖数: 3 | 6 Let's assume the mean and std of group one are A and a, respective.
Accordingly, the mean and std of group two are B and b, respectively. The
mean of group one divided by group two equals A/B, whereas the std of the
ratio equals (A/B)*[(a/A)^2+(b/B)^2]^0.5.
56,
the
SD
【在 h*********g 的大作中提到】
: I have 2 groups of data, e.g. group one is 1,2,1,3,4, group two is 45,46,56,
: 34,40. I want to calculate the ratio (group two/group one). I will take the
: means of the two groups and calculate the ratio. How do I get the SEM or SD
: of the ratios? Thanks.
|
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