绘制卡方分布

def solve():
    import numpy as np
    from scipy import stats
    from sklearn.datasets import load_iris
    iris = load_iris()
    sepal_length = iris.data[:, 0]
    n = len(sepal_length)
    std = np.std(sepal_length, ddof=1)
    # 方差的卡方置信区间
    chi2_low = stats.chi2.ppf(0.025, df=n-1)
    chi2_high = stats.chi2.ppf(0.975, df=n-1)
    ci_low = (n-1)*std**2 / chi2_high
    ci_high = (n-1)*std**2 / chi2_low
    print(f'{ci_low:.4f},{ci_high:.4f}')