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Minitab: Fitted Mean Calculation?

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This topic contains 5 replies, has 4 voices, and was last updated by  Jennifer Atlas 1 year, 11 months ago.

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  • #55773

    Earl
    Participant

    Hello,

    This is a person relatively new to Minitab and would really like some help. When doing an ANOVA test, I receive the fitted means for the sets of data. These fitted means are definitely different than the means of the data, but I am unfamiliar with how Minitab even obtains these values. I would greatly appreciate if someone could tell me how these numbers originate.

    Thanks!

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    #201671

    Chris Seider
    Participant

    When doing the One-way ANOVA, the means are the means of the groups associated with the factors.

    @joelatminitab who’s your replacement again? can’t remember!

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    #201672

    Bonnie Stone
    Participant

    Good question: Data means are the raw response variable means for each factor level combination whereas fitted means use least squares to predict the mean response values of a balanced design. Therefore, the two types of means are identical for balanced designs but can be different for unbalanced designs.

    Fitted means are useful for assessing response differences due to changes in factor levels rather than differences due to the unbalanced experimental conditions. While you can use raw data with unbalanced designs to obtain a general idea of which main effects may be evident, it is generally good practice to use the fitted means to obtain more precise results.

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    #201673

    Earl
    Participant

    Ah, I see. Thank you! Though, how would one go about calculating the fitted means using the least squares in an unbalanced design? I am personally trying to understand the process or the logic behind as to how Minitab obtains these results.

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    #201674

    Bonnie Stone
    Participant

    Which ANOVA tool are you using for your analysis?

    0
    #201676

    Jennifer Atlas
    Participant
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