Agronomy4future

When you conduct PCA (Principal Components Analysis), do you simply accept the result which software programs provide? If we just accept results without any doubts, we never understand the principle of PCA. In this time, I’ll introduce how PCA is calculated step by step, and if you read this post, I believe you can fully understand the concept of PCA. Here is one data. Let’s say we measured kernel number per ear (KN), average of kernel weight per ear (KW)…

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The reason why we use t-test, not z-test is because we don’t know the variance (σ2) of the population. The sample mean (x̅) is an unbiased estimator for the population mean (μ), and therefore we can estimate μ from x̅ (E(x̅) = μ). How about variance? If we know σ2, sample variance could be estimated by dividing σ2 by sample size (n); σ2x̄ = σ2/n. However, if we don’t know σ2, we should use standard deviation (s) of samples; s2x̄ = s2/n…

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New equation I suggest!! You might be already familiar with how to calculate pooled variance. This story is about pooled variance when blocks exist. If you run statistics programs, you’ll simply obtain pooled variance (also known as MSE), but you’ll never understand the concept of pooled variance if you just run software programs. Here is an example data. Let’s say this is a yield data. Cultivar A Cultivar B 120 70 130 90 110 50 Mean: 120Variance (s2): 100 Mean:…

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Previous post□ What is ANCOVA (1/3)? The basic concept□ What is ANCOVA (2/3)? How to interpret Parameter Estimates In the previous posts, I explained the basic concept of ANCOVA and how to interpret statistical results. Now, I will discuss the most important concept that is not commonly mentioned. The statistical program provided the following model in the previous posts. Control: y= 9.53 + 0.0558 xFast: y= 6.39 + 0.0558 xSlow: y= 13.10 + 0.0558 x Then, if we apply the mean…

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여기 x 와 y 에 대한 데이터가 있습니다. x 가 변화함에 따라 y 는 어떻게 달라지는지를 알고 싶어 회귀분석을 해 보겠습니다. x y 1 10 30 2 20 40 3 30 50 4 40 80 5 50 90 6 60 100 7 70 120 저는 SAS 를 이용합니다. 먼저 데이터 데이블을 생성합니다. 그리고 단순선형 회귀분석을 해 보겠습니다. 통계 프로그램은 회귀방정식 y= 11.429 + 1.5357x 를 제공해 주었습니다. 즉, x 가 1 증가할 때 y 는1.5357 배로 증가합니다. 그리고 이 회귀모형의…

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